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SpeculateAroundPHIs: Respect convergent 

llvm-svn: 361957
This commit is contained in:
Matt Arsenault 2019-05-29 13:14:39 +00:00
parent 9ffd8b5a6f
commit 36e7254441
2 changed files with 106 additions and 0 deletions
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8
llvm/lib/Transforms/Scalar/SpeculateAroundPHIs.cpp
View File

@ -67,6 +67,14 @@ isSafeToSpeculatePHIUsers(PHINode &PN, DominatorTree &DT,
return false;
}
if (auto CS = ImmutableCallSite(UI)) {
if (CS.isConvergent() || CS.cannotDuplicate()) {
LLVM_DEBUG(dbgs() << " Unsafe: convergent "
"callsite cannot de duplicated: " << *UI << '\n');
return false;
}
}
// FIXME: This check is much too conservative. We're not going to move these
// instructions onto new dynamic paths through the program unless there is
// a call instruction between the use and the PHI node. And memory isn't

98
llvm/test/Transforms/SpeculateAroundPHIs/convergent.ll Normal file
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@ -0,0 +1,98 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt -S -passes=spec-phis < %s | FileCheck %s
; Make sure convergent and noduplicate calls aren't duplicated.
declare i32 @llvm.convergent(i32) #0
declare i32 @llvm.noduplicate(i32) #1
declare i32 @llvm.regular(i32) #2
define i32 @test_convergent(i1 %flag, i32 %arg) #0 {
; CHECK-LABEL: @test_convergent(
; CHECK-NEXT: entry:
; CHECK-NEXT: br i1 [[FLAG:%.*]], label [[A:%.*]], label [[B:%.*]]
; CHECK: a:
; CHECK-NEXT: br label [[EXIT:%.*]]
; CHECK: b:
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
; CHECK-NEXT: [[P:%.*]] = phi i32 [ 7, [[A]] ], [ 11, [[B]] ]
; CHECK-NEXT: [[SUM:%.*]] = call i32 @llvm.convergent(i32 [[P]])
; CHECK-NEXT: ret i32 [[SUM]]
;
entry:
br i1 %flag, label %a, label %b
a:
br label %exit
b:
br label %exit
exit:
%p = phi i32 [ 7, %a ], [ 11, %b ]
%sum = call i32 @llvm.convergent(i32 %p)
ret i32 %sum
}
define i32 @test_noduplicate(i1 %flag, i32 %arg) #1 {
; CHECK-LABEL: @test_noduplicate(
; CHECK-NEXT: entry:
; CHECK-NEXT: br i1 [[FLAG:%.*]], label [[A:%.*]], label [[B:%.*]]
; CHECK: a:
; CHECK-NEXT: br label [[EXIT:%.*]]
; CHECK: b:
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
; CHECK-NEXT: [[P:%.*]] = phi i32 [ 7, [[A]] ], [ 11, [[B]] ]
; CHECK-NEXT: [[SUM:%.*]] = call i32 @llvm.noduplicate(i32 [[P]])
; CHECK-NEXT: ret i32 [[SUM]]
;
entry:
br i1 %flag, label %a, label %b
a:
br label %exit
b:
br label %exit
exit:
%p = phi i32 [ 7, %a ], [ 11, %b ]
%sum = call i32 @llvm.noduplicate(i32 %p)
ret i32 %sum
}
; Otherwise identical function which should be transformed.
define i32 @test_reference(i1 %flag, i32 %arg) #2 {
; CHECK-LABEL: @test_reference(
; CHECK-NEXT: entry:
; CHECK-NEXT: br i1 [[FLAG:%.*]], label [[A:%.*]], label [[B:%.*]]
; CHECK: a:
; CHECK-NEXT: [[SUM_0:%.*]] = call i32 @llvm.regular(i32 7)
; CHECK-NEXT: br label [[EXIT:%.*]]
; CHECK: b:
; CHECK-NEXT: [[SUM_1:%.*]] = call i32 @llvm.regular(i32 11)
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
; CHECK-NEXT: [[SUM_PHI:%.*]] = phi i32 [ [[SUM_0]], [[A]] ], [ [[SUM_1]], [[B]] ]
; CHECK-NEXT: ret i32 [[SUM_PHI]]
;
entry:
br i1 %flag, label %a, label %b
a:
br label %exit
b:
br label %exit
exit:
%p = phi i32 [ 7, %a ], [ 11, %b ]
%sum = call i32 @llvm.regular(i32 %p)
ret i32 %sum
}
attributes #0 = { nounwind readnone convergent speculatable }
attributes #1 = { nounwind readnone noduplicate speculatable }
attributes #2 = { nounwind readnone speculatable }