380fa875ab
This patch replaces all dominated uses of condition with true/false to
improve context-sensitive optimizations. It eliminates a bunch of
branches in llvm-opt-benchmark.
As a side effect, it may introduce new phi nodes in some corner cases.
See the following case:
```
define i1 @test(i1 %cmp, i1 %cond) {
entry:
br i1 %cond, label %bb1, label %bb2
bb1:
br i1 %cmp, label %if.then, label %if.else
if.then:
br %bb2
if.else:
br %bb2
bb2:
%res = phi i1 [%cmp, %entry], [%cmp, %if.then], [%cmp, %if.else]
ret i1 %res
}
```
It will be simplified into:
```
define i1 @test(i1 %cmp, i1 %cond) {
entry:
br i1 %cond, label %bb1, label %bb2
bb1:
br i1 %cmp, label %if.then, label %if.else
if.then:
br %bb2
if.else:
br %bb2
bb2:
%res = phi i1 [%cmp, %entry], [true, %if.then], [false, %if.else]
ret i1 %res
}
```
I am planning to fix this in late pipeline/CGP since this problem exists
before the patch.
48 lines
1.6 KiB
LLVM
48 lines
1.6 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
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; RUN: opt -O3 -S < %s | FileCheck %s
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define void @growTables(ptr %p) {
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; CHECK-LABEL: define void @growTables(
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; CHECK-SAME: ptr [[P:%.*]]) local_unnamed_addr #[[ATTR0:[0-9]+]] {
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; CHECK-NEXT: [[ENTRY:.*]]:
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; CHECK-NEXT: [[CALL:%.*]] = load volatile i32, ptr [[P]], align 4
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; CHECK-NEXT: [[CMP71:%.*]] = icmp sgt i32 [[CALL]], 0
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; CHECK-NEXT: br i1 [[CMP71]], label %[[FOR_BODY:.*]], label %[[COMMON_RET:.*]]
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; CHECK: [[FOR_BODY]]:
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; CHECK-NEXT: [[I_02:%.*]] = phi i32 [ [[INC:%.*]], %[[FOR_BODY]] ], [ 0, %[[ENTRY]] ]
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; CHECK-NEXT: [[CALL9:%.*]] = load volatile ptr, ptr [[P]], align 8
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; CHECK-NEXT: [[INC]] = add nuw nsw i32 [[I_02]], 1
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; CHECK-NEXT: [[CMP7:%.*]] = icmp slt i32 [[INC]], [[CALL]]
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; CHECK-NEXT: br i1 [[CMP7]], label %[[FOR_BODY]], label %[[FOR_BODY12:.*]]
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; CHECK: [[FOR_BODY12]]:
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; CHECK-NEXT: [[CALL14:%.*]] = load volatile ptr, ptr [[P]], align 8
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; CHECK-NEXT: br label %[[COMMON_RET]]
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; CHECK: [[COMMON_RET]]:
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; CHECK-NEXT: ret void
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;
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entry:
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%call = load volatile i32, ptr %p, align 4
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br label %for.cond
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for.cond:
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%i.0 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
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%cmp7 = icmp slt i32 %i.0, %call
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br i1 %cmp7, label %for.body, label %for.end
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for.body:
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%call9 = load volatile ptr, ptr %p, align 8
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%inc = add i32 %i.0, 1
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br label %for.cond
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for.end:
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%cmp11 = icmp sgt i32 %call, 0
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br i1 %cmp11, label %for.body12, label %common.ret
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for.body12:
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%call14 = load volatile ptr, ptr %p, align 8
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br label %common.ret
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common.ret:
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ret void
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}
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