88cad7e5cf
This was a real restriction in the original version of SinkIfThenCodeToEnd. Now it's been rewritten, the restriction can be lifted.
As part of this, we handle a very common and useful case where one of the incoming branches is actually conditional. Consider:
if (a)
x(1);
else if (b)
x(2);
This produces the following CFG:
[if]
/ \
[x(1)] [if]
| | \
| | \
| [x(2)] |
\ | /
[ end ]
[end] has two unconditional predecessor arcs and one conditional. The conditional refers to the implicit empty 'else' arc. This same pattern can also be caused by an empty default block in a switch.
We can't sink the call to x() down to end because no call to x() happens on the third incoming arc (assume that x() has sideeffects for the sake of argument; if something is safe to speculate we could indeed sink nevertheless but this cannot happen in the general case and causes many extra selects).
We are now able to detect this case and split off the unconditional arcs to a common successor:
[if]
/ \
[x(1)] [if]
| | \
| | \
| [x(2)] |
\ / |
[sink.split] |
\ /
[ end ]
Now we can sink the call to x() into %sink.split. This can cause significant code simplification in many testcases.
llvm-svn: 280364
568 lines
12 KiB
LLVM
568 lines
12 KiB
LLVM
; RUN: opt < %s -simplifycfg -S | FileCheck %s
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define zeroext i1 @test1(i1 zeroext %flag, i32 %blksA, i32 %blksB, i32 %nblks) {
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entry:
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br i1 %flag, label %if.then, label %if.else
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; CHECK-LABEL: test1
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; CHECK: add
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; CHECK: select
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; CHECK: icmp
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; CHECK-NOT: br
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if.then:
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%cmp = icmp uge i32 %blksA, %nblks
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%frombool1 = zext i1 %cmp to i8
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br label %if.end
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if.else:
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%add = add i32 %nblks, %blksB
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%cmp2 = icmp ule i32 %add, %blksA
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%frombool3 = zext i1 %cmp2 to i8
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br label %if.end
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if.end:
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%obeys.0 = phi i8 [ %frombool1, %if.then ], [ %frombool3, %if.else ]
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%tobool4 = icmp ne i8 %obeys.0, 0
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ret i1 %tobool4
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}
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define zeroext i1 @test2(i1 zeroext %flag, i32 %blksA, i32 %blksB, i32 %nblks) {
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entry:
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br i1 %flag, label %if.then, label %if.else
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; CHECK-LABEL: test2
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; CHECK: add
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; CHECK: select
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; CHECK: icmp
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; CHECK-NOT: br
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if.then:
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%cmp = icmp uge i32 %blksA, %nblks
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%frombool1 = zext i1 %cmp to i8
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br label %if.end
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if.else:
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%add = add i32 %nblks, %blksB
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%cmp2 = icmp uge i32 %blksA, %add
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%frombool3 = zext i1 %cmp2 to i8
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br label %if.end
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if.end:
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%obeys.0 = phi i8 [ %frombool1, %if.then ], [ %frombool3, %if.else ]
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%tobool4 = icmp ne i8 %obeys.0, 0
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ret i1 %tobool4
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}
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declare i32 @foo(i32, i32) nounwind readnone
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define i32 @test3(i1 zeroext %flag, i32 %x, i32 %y) {
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entry:
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br i1 %flag, label %if.then, label %if.else
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if.then:
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%x0 = call i32 @foo(i32 %x, i32 0) nounwind readnone
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%y0 = call i32 @foo(i32 %x, i32 1) nounwind readnone
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br label %if.end
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if.else:
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%x1 = call i32 @foo(i32 %y, i32 0) nounwind readnone
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%y1 = call i32 @foo(i32 %y, i32 1) nounwind readnone
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br label %if.end
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if.end:
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%xx = phi i32 [ %x0, %if.then ], [ %x1, %if.else ]
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%yy = phi i32 [ %y0, %if.then ], [ %y1, %if.else ]
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%ret = add i32 %xx, %yy
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ret i32 %ret
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}
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; CHECK-LABEL: test3
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; CHECK: select
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; CHECK: call
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; CHECK: call
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; CHECK: add
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; CHECK-NOT: br
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define i32 @test4(i1 zeroext %flag, i32 %x, i32* %y) {
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entry:
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br i1 %flag, label %if.then, label %if.else
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if.then:
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%a = add i32 %x, 5
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store i32 %a, i32* %y
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br label %if.end
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if.else:
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%b = add i32 %x, 7
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store i32 %b, i32* %y
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br label %if.end
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if.end:
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ret i32 1
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}
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; CHECK-LABEL: test4
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; CHECK: select
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; CHECK: store
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; CHECK-NOT: store
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define i32 @test5(i1 zeroext %flag, i32 %x, i32* %y) {
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entry:
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br i1 %flag, label %if.then, label %if.else
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if.then:
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%a = add i32 %x, 5
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store volatile i32 %a, i32* %y
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br label %if.end
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if.else:
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%b = add i32 %x, 7
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store i32 %b, i32* %y
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br label %if.end
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if.end:
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ret i32 1
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}
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; CHECK-LABEL: test5
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; CHECK: store volatile
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; CHECK: store
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define i32 @test6(i1 zeroext %flag, i32 %x, i32* %y) {
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entry:
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br i1 %flag, label %if.then, label %if.else
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if.then:
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%a = add i32 %x, 5
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store volatile i32 %a, i32* %y
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br label %if.end
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if.else:
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%b = add i32 %x, 7
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store volatile i32 %b, i32* %y
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br label %if.end
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if.end:
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ret i32 1
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}
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; CHECK-LABEL: test6
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; CHECK: select
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; CHECK: store volatile
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; CHECK-NOT: store
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define i32 @test7(i1 zeroext %flag, i32 %x, i32* %y) {
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entry:
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br i1 %flag, label %if.then, label %if.else
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if.then:
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%z = load volatile i32, i32* %y
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%a = add i32 %z, 5
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store volatile i32 %a, i32* %y
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br label %if.end
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if.else:
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%w = load volatile i32, i32* %y
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%b = add i32 %w, 7
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store volatile i32 %b, i32* %y
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br label %if.end
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if.end:
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ret i32 1
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}
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; CHECK-LABEL: test7
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; CHECK-DAG: select
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; CHECK-DAG: load volatile
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; CHECK: store volatile
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; CHECK-NOT: load
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; CHECK-NOT: store
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; %z and %w are in different blocks. We shouldn't sink the add because
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; there may be intervening memory instructions.
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define i32 @test8(i1 zeroext %flag, i32 %x, i32* %y) {
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entry:
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%z = load volatile i32, i32* %y
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br i1 %flag, label %if.then, label %if.else
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if.then:
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%a = add i32 %z, 5
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store volatile i32 %a, i32* %y
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br label %if.end
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if.else:
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%w = load volatile i32, i32* %y
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%b = add i32 %w, 7
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store volatile i32 %b, i32* %y
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br label %if.end
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if.end:
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ret i32 1
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}
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; CHECK-LABEL: test8
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; CHECK: add
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; CHECK: add
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; The extra store in %if.then means %z and %w are not equivalent.
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define i32 @test9(i1 zeroext %flag, i32 %x, i32* %y, i32* %p) {
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entry:
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br i1 %flag, label %if.then, label %if.else
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if.then:
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store i32 7, i32* %p
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%z = load volatile i32, i32* %y
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store i32 6, i32* %p
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%a = add i32 %z, 5
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store volatile i32 %a, i32* %y
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br label %if.end
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if.else:
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%w = load volatile i32, i32* %y
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%b = add i32 %w, 7
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store volatile i32 %b, i32* %y
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br label %if.end
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if.end:
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ret i32 1
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}
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; CHECK-LABEL: test9
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; CHECK: add
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; CHECK: add
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%struct.anon = type { i32, i32 }
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; The GEP indexes a struct type so cannot have a variable last index.
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define i32 @test10(i1 zeroext %flag, i32 %x, i32* %y, %struct.anon* %s) {
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entry:
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br i1 %flag, label %if.then, label %if.else
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if.then:
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%dummy = add i32 %x, 5
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%gepa = getelementptr inbounds %struct.anon, %struct.anon* %s, i32 0, i32 0
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store volatile i32 %x, i32* %gepa
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br label %if.end
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if.else:
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%dummy1 = add i32 %x, 6
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%gepb = getelementptr inbounds %struct.anon, %struct.anon* %s, i32 0, i32 1
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store volatile i32 %x, i32* %gepb
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br label %if.end
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if.end:
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ret i32 1
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}
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; CHECK-LABEL: test10
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; CHECK: getelementptr
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; CHECK: getelementptr
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; CHECK: phi
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; CHECK: store volatile
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; The shufflevector's mask operand cannot be merged in a PHI.
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define i32 @test11(i1 zeroext %flag, i32 %w, <2 x i32> %x, <2 x i32> %y) {
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entry:
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br i1 %flag, label %if.then, label %if.else
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if.then:
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%dummy = add i32 %w, 5
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%sv1 = shufflevector <2 x i32> %x, <2 x i32> %y, <2 x i32> <i32 0, i32 1>
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br label %if.end
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if.else:
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%dummy1 = add i32 %w, 6
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%sv2 = shufflevector <2 x i32> %x, <2 x i32> %y, <2 x i32> <i32 1, i32 0>
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br label %if.end
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if.end:
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%p = phi <2 x i32> [ %sv1, %if.then ], [ %sv2, %if.else ]
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ret i32 1
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}
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; CHECK-LABEL: test11
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; CHECK: shufflevector
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; CHECK: shufflevector
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; We can't common an intrinsic!
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define i32 @test12(i1 zeroext %flag, i32 %w, i32 %x, i32 %y) {
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entry:
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br i1 %flag, label %if.then, label %if.else
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if.then:
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%dummy = add i32 %w, 5
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%sv1 = call i32 @llvm.ctlz.i32(i32 %x)
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br label %if.end
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if.else:
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%dummy1 = add i32 %w, 6
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%sv2 = call i32 @llvm.cttz.i32(i32 %x)
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br label %if.end
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if.end:
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%p = phi i32 [ %sv1, %if.then ], [ %sv2, %if.else ]
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ret i32 1
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}
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declare i32 @llvm.ctlz.i32(i32 %x) readnone
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declare i32 @llvm.cttz.i32(i32 %x) readnone
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; CHECK-LABEL: test12
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; CHECK: call i32 @llvm.ctlz
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; CHECK: call i32 @llvm.cttz
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; The TBAA metadata should be properly combined.
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define i32 @test13(i1 zeroext %flag, i32 %x, i32* %y) {
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entry:
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br i1 %flag, label %if.then, label %if.else
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if.then:
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%z = load volatile i32, i32* %y
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%a = add i32 %z, 5
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store volatile i32 %a, i32* %y, !tbaa !3
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br label %if.end
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if.else:
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%w = load volatile i32, i32* %y
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%b = add i32 %w, 7
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store volatile i32 %b, i32* %y, !tbaa !4
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br label %if.end
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if.end:
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ret i32 1
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}
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!0 = !{ !"an example type tree" }
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!1 = !{ !"int", !0 }
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!2 = !{ !"float", !0 }
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!3 = !{ !"const float", !2, i64 0 }
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!4 = !{ !"special float", !2, i64 1 }
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; CHECK-LABEL: test13
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; CHECK-DAG: select
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; CHECK-DAG: load volatile
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; CHECK: store volatile {{.*}}, !tbaa !0
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; CHECK-NOT: load
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; CHECK-NOT: store
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; The call should be commoned.
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define i32 @test13a(i1 zeroext %flag, i32 %w, i32 %x, i32 %y) {
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entry:
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br i1 %flag, label %if.then, label %if.else
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if.then:
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%sv1 = call i32 @bar(i32 %x)
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br label %if.end
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if.else:
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%sv2 = call i32 @bar(i32 %y)
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br label %if.end
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if.end:
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%p = phi i32 [ %sv1, %if.then ], [ %sv2, %if.else ]
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ret i32 1
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}
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declare i32 @bar(i32)
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; CHECK-LABEL: test13a
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; CHECK: %[[x:.*]] = select i1 %flag
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; CHECK: call i32 @bar(i32 %[[x]])
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; The load should be commoned.
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define i32 @test14(i1 zeroext %flag, i32 %w, i32 %x, i32 %y, %struct.anon* %s) {
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entry:
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br i1 %flag, label %if.then, label %if.else
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if.then:
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%dummy = add i32 %x, 1
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%gepa = getelementptr inbounds %struct.anon, %struct.anon* %s, i32 0, i32 1
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%sv1 = load i32, i32* %gepa
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%cmp1 = icmp eq i32 %sv1, 56
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br label %if.end
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if.else:
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%dummy2 = add i32 %x, 4
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%gepb = getelementptr inbounds %struct.anon, %struct.anon* %s, i32 0, i32 1
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%sv2 = load i32, i32* %gepb
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%cmp2 = icmp eq i32 %sv2, 57
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br label %if.end
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if.end:
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%p = phi i1 [ %cmp1, %if.then ], [ %cmp2, %if.else ]
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ret i32 1
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}
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; CHECK-LABEL: test14
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; CHECK: getelementptr
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; CHECK: load
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; CHECK-NOT: load
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; The load should be commoned.
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define i32 @test15(i1 zeroext %flag, i32 %w, i32 %x, i32 %y, %struct.anon* %s) {
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entry:
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br i1 %flag, label %if.then, label %if.else
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if.then:
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%dummy = add i32 %x, 1
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%gepa = getelementptr inbounds %struct.anon, %struct.anon* %s, i32 0, i32 0
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%sv1 = load i32, i32* %gepa
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%ext1 = zext i32 %sv1 to i64
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%cmp1 = icmp eq i64 %ext1, 56
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br label %if.end
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if.else:
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%dummy2 = add i32 %x, 4
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%gepb = getelementptr inbounds %struct.anon, %struct.anon* %s, i32 0, i32 1
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%sv2 = load i32, i32* %gepb
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%ext2 = zext i32 %sv2 to i64
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%cmp2 = icmp eq i64 %ext2, 57
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br label %if.end
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if.end:
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%p = phi i1 [ %cmp1, %if.then ], [ %cmp2, %if.else ]
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ret i32 1
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}
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; CHECK-LABEL: test15
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; CHECK: getelementptr
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; CHECK: load
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; CHECK-NOT: load
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define zeroext i1 @test_crash(i1 zeroext %flag, i32* %i4, i32* %m, i32* %n) {
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entry:
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br i1 %flag, label %if.then, label %if.else
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if.then:
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%tmp1 = load i32, i32* %i4
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%tmp2 = add i32 %tmp1, -1
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store i32 %tmp2, i32* %i4
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br label %if.end
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if.else:
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%tmp3 = load i32, i32* %m
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%tmp4 = load i32, i32* %n
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|
%tmp5 = add i32 %tmp3, %tmp4
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store i32 %tmp5, i32* %i4
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br label %if.end
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if.end:
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ret i1 true
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}
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|
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; CHECK-LABEL: test_crash
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|
; No checks for test_crash - just ensure it doesn't crash!
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|
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define zeroext i1 @test16(i1 zeroext %flag, i1 zeroext %flag2, i32 %blksA, i32 %blksB, i32 %nblks) {
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|
entry:
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|
br i1 %flag, label %if.then, label %if.else
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if.then:
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|
%cmp = icmp uge i32 %blksA, %nblks
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|
%frombool1 = zext i1 %cmp to i8
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|
br label %if.end
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|
if.else:
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|
br i1 %flag2, label %if.then2, label %if.end
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|
if.then2:
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|
%add = add i32 %nblks, %blksB
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|
%cmp2 = icmp ule i32 %add, %blksA
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|
%frombool3 = zext i1 %cmp2 to i8
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|
br label %if.end
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|
if.end:
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|
%obeys.0 = phi i8 [ %frombool1, %if.then ], [ %frombool3, %if.then2 ], [ 0, %if.else ]
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|
%tobool4 = icmp ne i8 %obeys.0, 0
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ret i1 %tobool4
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}
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|
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; CHECK-LABEL: test16
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|
; CHECK: zext
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; CHECK-NOT: zext
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|
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define zeroext i1 @test17(i32 %flag, i32 %blksA, i32 %blksB, i32 %nblks) {
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|
entry:
|
|
switch i32 %flag, label %if.end [
|
|
i32 0, label %if.then
|
|
i32 1, label %if.then2
|
|
]
|
|
|
|
if.then:
|
|
%cmp = icmp uge i32 %blksA, %nblks
|
|
%frombool1 = zext i1 %cmp to i8
|
|
br label %if.end
|
|
|
|
if.then2:
|
|
%add = add i32 %nblks, %blksB
|
|
%cmp2 = icmp ule i32 %add, %blksA
|
|
%frombool3 = zext i1 %cmp2 to i8
|
|
br label %if.end
|
|
|
|
if.end:
|
|
%obeys.0 = phi i8 [ %frombool1, %if.then ], [ %frombool3, %if.then2 ], [ 0, %entry ]
|
|
%tobool4 = icmp ne i8 %obeys.0, 0
|
|
ret i1 %tobool4
|
|
}
|
|
|
|
; CHECK-LABEL: test17
|
|
; CHECK: if.then:
|
|
; CHECK-NEXT: icmp uge
|
|
; CHECK-NEXT: br label %[[x:.*]]
|
|
|
|
; CHECK: if.then2:
|
|
; CHECK-NEXT: add
|
|
; CHECK-NEXT: icmp ule
|
|
; CHECK-NEXT: br label %[[x]]
|
|
|
|
; CHECK: [[x]]:
|
|
; CHECK-NEXT: %[[y:.*]] = phi i1 [ %cmp
|
|
; CHECK-NEXT: %[[z:.*]] = zext i1 %[[y]]
|
|
; CHECK-NEXT: br label %if.end
|
|
|
|
; CHECK: if.end:
|
|
; CHECK-NEXT: phi i8
|
|
; CHECK-DAG: [ %[[z]], %[[x]] ]
|
|
; CHECK-DAG: [ 0, %entry ]
|
|
|
|
define zeroext i1 @test18(i32 %flag, i32 %blksA, i32 %blksB, i32 %nblks) {
|
|
entry:
|
|
switch i32 %flag, label %if.then3 [
|
|
i32 0, label %if.then
|
|
i32 1, label %if.then2
|
|
]
|
|
|
|
if.then:
|
|
%cmp = icmp uge i32 %blksA, %nblks
|
|
%frombool1 = zext i1 %cmp to i8
|
|
br label %if.end
|
|
|
|
if.then2:
|
|
%add = add i32 %nblks, %blksB
|
|
%cmp2 = icmp ule i32 %add, %blksA
|
|
%frombool3 = zext i1 %cmp2 to i8
|
|
br label %if.end
|
|
|
|
if.then3:
|
|
%add2 = add i32 %nblks, %blksA
|
|
%cmp3 = icmp ule i32 %add2, %blksA
|
|
%frombool4 = zext i1 %cmp3 to i8
|
|
br label %if.end
|
|
|
|
if.end:
|
|
%obeys.0 = phi i8 [ %frombool1, %if.then ], [ %frombool3, %if.then2 ], [ %frombool4, %if.then3 ]
|
|
%tobool4 = icmp ne i8 %obeys.0, 0
|
|
ret i1 %tobool4
|
|
}
|
|
|
|
; CHECK-LABEL: test18
|
|
; CHECK: if.end:
|
|
; CHECK-NEXT: %[[x:.*]] = phi i1
|
|
; CHECK-DAG: [ %cmp, %if.then ]
|
|
; CHECK-DAG: [ %cmp2, %if.then2 ]
|
|
; CHECK-DAG: [ %cmp3, %if.then3 ]
|
|
; CHECK-NEXT: zext i1 %[[x]] to i8
|
|
|
|
; CHECK: !0 = !{!1, !1, i64 0}
|
|
; CHECK: !1 = !{!"float", !2}
|
|
; CHECK: !2 = !{!"an example type tree"}
|