a37bb4a65d
Summary:
This is a straightforward extension of what LoopUnswitch does to
branches to guards. That is, we unswitch
```
for (;;) {
...
guard(loop_invariant_cond);
...
}
```
into
```
if (loop_invariant_cond) {
for (;;) {
...
// There is no need to emit guard(true)
...
}
} else {
for (;;) {
...
guard(false);
// SimplifyCFG will clean this up by adding an
// unreachable after the guard(false)
...
}
}
```
Reviewers: majnemer
Subscribers: mcrosier, llvm-commits, mzolotukhin
Differential Revision: http://reviews.llvm.org/D21725
llvm-svn: 273801
98 lines
2.6 KiB
LLVM
98 lines
2.6 KiB
LLVM
; RUN: opt -S -loop-unswitch < %s | FileCheck %s
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declare void @llvm.experimental.guard(i1, ...)
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define void @f_0(i32 %n, i32* %ptr, i1 %c) {
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; CHECK-LABEL: @f_0(
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; CHECK: loop.us:
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; CHECK-NOT: guard
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; CHECK: loop:
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; CHECK: call void (i1, ...) @llvm.experimental.guard(i1 false) [ "deopt"() ]
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entry:
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br label %loop
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loop:
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%iv = phi i32 [ 0, %entry ], [ %iv.inc, %loop ]
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%iv.inc = add i32 %iv, 1
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call void(i1, ...) @llvm.experimental.guard(i1 %c) [ "deopt"() ]
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store volatile i32 0, i32* %ptr
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%becond = icmp ult i32 %iv.inc, %n
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br i1 %becond, label %leave, label %loop
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leave:
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ret void
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}
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define void @f_1(i32 %n, i32* %ptr, i1 %c_0, i1 %c_1) {
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; CHECK-LABEL: @f_1(
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; CHECK: loop.us.us:
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; CHECK-NOT: guard
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; CHECK: loop.us:
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; CHECK: call void (i1, ...) @llvm.experimental.guard(i1 false) [ "deopt"(i32 2) ]
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; CHECK-NOT: guard
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; CHECK: loop.us1:
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; CHECK: call void (i1, ...) @llvm.experimental.guard(i1 false) [ "deopt"(i32 1) ]
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; CHECK-NOT: guard
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; CHECK: loop:
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; CHECK: call void (i1, ...) @llvm.experimental.guard(i1 false) [ "deopt"(i32 1) ]
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; CHECK: call void (i1, ...) @llvm.experimental.guard(i1 false) [ "deopt"(i32 2) ]
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entry:
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br label %loop
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loop:
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%iv = phi i32 [ 0, %entry ], [ %iv.inc, %loop ]
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%iv.inc = add i32 %iv, 1
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call void(i1, ...) @llvm.experimental.guard(i1 %c_0) [ "deopt"(i32 1) ]
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store volatile i32 0, i32* %ptr
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call void(i1, ...) @llvm.experimental.guard(i1 %c_1) [ "deopt"(i32 2) ]
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%becond = icmp ult i32 %iv.inc, %n
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br i1 %becond, label %leave, label %loop
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leave:
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ret void
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}
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; Basic negative test
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define void @f_3(i32 %n, i32* %ptr, i1* %c_ptr) {
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; CHECK-LABEL: @f_3(
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; CHECK-NOT: loop.us:
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entry:
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br label %loop
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loop:
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%iv = phi i32 [ 0, %entry ], [ %iv.inc, %loop ]
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%iv.inc = add i32 %iv, 1
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%c = load volatile i1, i1* %c_ptr
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call void(i1, ...) @llvm.experimental.guard(i1 %c) [ "deopt"() ]
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store volatile i32 0, i32* %ptr
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%becond = icmp ult i32 %iv.inc, %n
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br i1 %becond, label %leave, label %loop
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leave:
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ret void
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}
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define void @f_4(i32 %n, i32* %ptr, i1 %c) {
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; CHECK-LABEL: @f_4(
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;
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; Demonstrate that unswitching on one guard can cause another guard to
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; be erased (this has implications on what guards we can keep raw
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; pointers to).
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entry:
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br label %loop
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loop:
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%iv = phi i32 [ 0, %entry ], [ %iv.inc, %loop ]
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%iv.inc = add i32 %iv, 1
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call void(i1, ...) @llvm.experimental.guard(i1 %c) [ "deopt"(i32 1) ]
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store volatile i32 0, i32* %ptr
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%neg = xor i1 %c, 1
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call void(i1, ...) @llvm.experimental.guard(i1 %neg) [ "deopt"(i32 2) ]
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%becond = icmp ult i32 %iv.inc, %n
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br i1 %becond, label %leave, label %loop
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leave:
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ret void
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}
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