ba45453c0a
- This patch skips the threading on known values if the target has
divergent branch.
- So far, threading on known values is skipped when the basic block has
covergent calls. However, even without convergent calls, if that
condition is divergent, threading duplicates the execution of that
block threaded and hence results in lower performance. E.g.,
```
BB1:
if (cond) BB3, BB2
BB2:
// work2
br BB3
BB3:
// work3
if (cond) BB5, BB4
BB4:
// work4
br BB5
BB5:
```
after threading,
```
BB1:
if (cond) BB3', BB2'
BB2':
// work3
br BB5
BB3':
// work2
// work3
// work4
br BB5
BB5:
```
After threading, work3 is executed twice if 'cond' is a divergent one.
Reviewers: yxsamliu, nikic
Pull Request: https://github.com/llvm/llvm-project/pull/100185
45 lines
1.1 KiB
LLVM
45 lines
1.1 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
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; RUN: opt -mtriple=amdgcn -S -passes=simplifycfg < %s | FileCheck %s
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declare void @bar1()
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declare void @bar2()
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declare void @bar3()
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define i32 @test_01a(i32 %a) {
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; CHECK-LABEL: define i32 @test_01a(
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; CHECK-SAME: i32 [[A:%.*]]) {
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; CHECK-NEXT: [[ENTRY:.*:]]
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; CHECK-NEXT: [[COND:%.*]] = icmp eq i32 [[A]], 0
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; CHECK-NEXT: br i1 [[COND]], label %[[MERGE:.*]], label %[[IF_FALSE:.*]]
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; CHECK: [[IF_FALSE]]:
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; CHECK-NEXT: call void @bar1()
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; CHECK-NEXT: br label %[[MERGE]]
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; CHECK: [[MERGE]]:
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; CHECK-NEXT: call void @bar2()
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; CHECK-NEXT: br i1 [[COND]], label %[[EXIT:.*]], label %[[IF_FALSE_2:.*]]
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; CHECK: [[IF_FALSE_2]]:
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; CHECK-NEXT: call void @bar3()
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; CHECK-NEXT: br label %[[EXIT]]
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; CHECK: [[EXIT]]:
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; CHECK-NEXT: ret i32 [[A]]
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;
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entry:
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%cond = icmp eq i32 %a, 0
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br i1 %cond, label %merge, label %if.false
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if.false:
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call void @bar1()
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br label %merge
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merge:
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call void @bar2()
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br i1 %cond, label %exit, label %if.false.2
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if.false.2:
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call void @bar3()
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br label %exit
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exit:
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ret i32 %a
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}
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