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[JumpThreading] PRE unordered loads

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Summary: Extend JumpThreading's PRE to unordered atomic loads.

Reviewers: hfinkel, reames

Subscribers: mcrosier, llvm-commits

Differential Revision: http://reviews.llvm.org/D22326

llvm-svn: 275456
This commit is contained in:
Sanjoy Das 2016-07-14 19:21:15 +00:00
parent 31ceba7c44
commit 13623ad009
2 changed files with 145 additions and 5 deletions
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11
llvm/lib/Transforms/Scalar/JumpThreading.cpp
View File

@ -924,8 +924,8 @@ bool JumpThreadingPass::ProcessImpliedCondition(BasicBlock *BB) {
/// important optimization that encourages jump threading, and needs to be run
/// interlaced with other jump threading tasks.
bool JumpThreadingPass::SimplifyPartiallyRedundantLoad(LoadInst *LI) {
// Don't hack volatile/atomic loads.
if (!LI->isSimple()) return false;
// Don't hack volatile and ordered loads.
if (!LI->isUnordered()) return false;
// If the load is defined in a block with exactly one predecessor, it can't be
// partially redundant.
@ -1055,9 +1055,10 @@ bool JumpThreadingPass::SimplifyPartiallyRedundantLoad(LoadInst *LI) {
if (UnavailablePred) {
assert(UnavailablePred->getTerminator()->getNumSuccessors() == 1 &&
"Can't handle critical edge here!");
LoadInst *NewVal = new LoadInst(LoadedPtr, LI->getName()+".pr", false,
LI->getAlignment(),
UnavailablePred->getTerminator());
LoadInst *NewVal =
new LoadInst(LoadedPtr, LI->getName() + ".pr", false,
LI->getAlignment(), LI->getOrdering(), LI->getSynchScope(),
UnavailablePred->getTerminator());
NewVal->setDebugLoc(LI->getDebugLoc());
if (AATags)
NewVal->setAAMetadata(AATags);

139
llvm/test/Transforms/JumpThreading/thread-loads.ll
View File

@ -107,6 +107,145 @@ return:
ret i32 13
}
define i32 @test4(i32* %P) {
; CHECK-LABEL: @test4(
entry:
%v0 = tail call i32 (...) @f1()
%v1 = icmp eq i32 %v0, 0
br i1 %v1, label %bb1, label %bb
bb:
; CHECK: bb1.thread:
; CHECK: store atomic
; CHECK: br label %bb3
store atomic i32 42, i32* %P unordered, align 4
br label %bb1
bb1:
; CHECK: bb1:
; CHECK-NOT: phi
; CHECK: load atomic
%res.0 = phi i32 [ 1, %bb ], [ 0, %entry ]
%v2 = load atomic i32, i32* %P unordered, align 4
%v3 = icmp sgt i32 %v2, 36
br i1 %v3, label %bb3, label %bb2
bb2:
%v4 = tail call i32 (...) @f2()
ret i32 %res.0
bb3:
ret i32 %res.0
}
define i32 @test5(i32* %P) {
; Negative test
; CHECK-LABEL: @test5(
entry:
%v0 = tail call i32 (...) @f1()
%v1 = icmp eq i32 %v0, 0
br i1 %v1, label %bb1, label %bb
bb:
; CHECK: bb:
; CHECK-NEXT: store atomic i32 42, i32* %P release, align 4
; CHECK-NEXT: br label %bb1
store atomic i32 42, i32* %P release, align 4
br label %bb1
bb1:
; CHECK: bb1:
; CHECK-NEXT: %res.0 = phi i32 [ 1, %bb ], [ 0, %entry ]
; CHECK-NEXT: %v2 = load atomic i32, i32* %P acquire, align 4
; CHECK-NEXT: %v3 = icmp sgt i32 %v2, 36
; CHECK-NEXT: br i1 %v3, label %bb3, label %bb2
%res.0 = phi i32 [ 1, %bb ], [ 0, %entry ]
%v2 = load atomic i32, i32* %P acquire, align 4
%v3 = icmp sgt i32 %v2, 36
br i1 %v3, label %bb3, label %bb2
bb2:
%v4 = tail call i32 (...) @f2()
ret i32 %res.0
bb3:
ret i32 %res.0
}
define i32 @test6(i32* %P) {
; Negative test
; CHECK-LABEL: @test6(
entry:
%v0 = tail call i32 (...) @f1()
%v1 = icmp eq i32 %v0, 0
br i1 %v1, label %bb1, label %bb
bb:
; CHECK: bb:
; CHECK-NEXT: store i32 42, i32* %P
; CHECK-NEXT: br label %bb1
store i32 42, i32* %P
br label %bb1
bb1:
; CHECK: bb1:
; CHECK-NEXT: %res.0 = phi i32 [ 1, %bb ], [ 0, %entry ]
; CHECK-NEXT: %v2 = load atomic i32, i32* %P acquire, align 4
; CHECK-NEXT: %v3 = icmp sgt i32 %v2, 36
; CHECK-NEXT: br i1 %v3, label %bb3, label %bb2
%res.0 = phi i32 [ 1, %bb ], [ 0, %entry ]
%v2 = load atomic i32, i32* %P acquire, align 4
%v3 = icmp sgt i32 %v2, 36
br i1 %v3, label %bb3, label %bb2
bb2:
%v4 = tail call i32 (...) @f2()
ret i32 %res.0
bb3:
ret i32 %res.0
}
define i32 @test7(i32* %P) {
; Negative test
; CHECK-LABEL: @test7(
entry:
%v0 = tail call i32 (...) @f1()
%v1 = icmp eq i32 %v0, 0
br i1 %v1, label %bb1, label %bb
bb:
; CHECK: bb:
; CHECK-NEXT: %val = load i32, i32* %P
; CHECK-NEXT: br label %bb1
%val = load i32, i32* %P
br label %bb1
bb1:
; CHECK: bb1:
; CHECK-NEXT: %res.0 = phi i32 [ 1, %bb ], [ 0, %entry ]
; CHECK-NEXT: %v2 = load atomic i32, i32* %P acquire, align 4
; CHECK-NEXT: %v3 = icmp sgt i32 %v2, 36
; CHECK-NEXT: br i1 %v3, label %bb3, label %bb2
%res.0 = phi i32 [ 1, %bb ], [ 0, %entry ]
%v2 = load atomic i32, i32* %P acquire, align 4
%v3 = icmp sgt i32 %v2, 36
br i1 %v3, label %bb3, label %bb2
bb2:
%v4 = tail call i32 (...) @f2()
ret i32 %res.0
bb3:
ret i32 %res.0
}
!0 = !{!3, !3, i64 0}
!1 = !{!"omnipotent char", !2}
!2 = !{!"Simple C/C++ TBAA", null}