[llvm] r246415 - [JumpThreading] make jump threading respect convergent annotation.
Jingyue Wu via llvm-commits
llvm-commits at lists.llvm.org
Sun Aug 30 23:10:27 PDT 2015
Author: jingyue
Date: Mon Aug 31 01:10:27 2015
New Revision: 246415
URL: http://llvm.org/viewvc/llvm-project?rev=246415&view=rev
Log:
[JumpThreading] make jump threading respect convergent annotation.
Summary:
JumpThreading shouldn't duplicate a convergent call, because that would move a convergent call into a control-inequivalent location. For example,
if (cond) {
...
} else {
...
}
convergent_call();
if (cond) {
...
} else {
...
}
should not be optimized to
if (cond) {
...
convergent_call();
...
} else {
...
convergent_call();
...
}
Test Plan: test/Transforms/JumpThreading/basic.ll
Patch by Xuetian Weng.
Reviewers: resistor, arsenm, jingyue
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D12484
Modified:
llvm/trunk/include/llvm/IR/Instructions.h
llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp
llvm/trunk/test/Transforms/JumpThreading/basic.ll
Modified: llvm/trunk/include/llvm/IR/Instructions.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/IR/Instructions.h?rev=246415&r1=246414&r2=246415&view=diff
==============================================================================
--- llvm/trunk/include/llvm/IR/Instructions.h (original)
+++ llvm/trunk/include/llvm/IR/Instructions.h Mon Aug 31 01:10:27 2015
@@ -1634,6 +1634,12 @@ public:
addAttribute(AttributeSet::FunctionIndex, Attribute::NoDuplicate);
}
+ /// \brief Determine if the call is convergent
+ bool isConvergent() const { return hasFnAttr(Attribute::Convergent); }
+ void setConvergent() {
+ addAttribute(AttributeSet::FunctionIndex, Attribute::Convergent);
+ }
+
/// \brief Determine if the call returns a structure through first
/// pointer argument.
bool hasStructRetAttr() const {
Modified: llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp?rev=246415&r1=246414&r2=246415&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp Mon Aug 31 01:10:27 2015
@@ -273,7 +273,7 @@ static unsigned getJumpThreadDuplication
// as having cost of 2 total, and if they are a vector intrinsic, we model
// them as having cost 1.
if (const CallInst *CI = dyn_cast<CallInst>(I)) {
- if (CI->cannotDuplicate())
+ if (CI->cannotDuplicate() || CI->isConvergent())
// Blocks with NoDuplicate are modelled as having infinite cost, so they
// are never duplicated.
return ~0U;
Modified: llvm/trunk/test/Transforms/JumpThreading/basic.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/JumpThreading/basic.ll?rev=246415&r1=246414&r2=246415&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/JumpThreading/basic.ll (original)
+++ llvm/trunk/test/Transforms/JumpThreading/basic.ll Mon Aug 31 01:10:27 2015
@@ -483,7 +483,7 @@ declare void @g()
declare void @j()
declare void @k()
-; CHECK: define void @h(i32 %p) {
+; CHECK-LABEL: define void @h(i32 %p) {
define void @h(i32 %p) {
%x = icmp ult i32 %p, 5
br i1 %x, label %l1, label %l2
@@ -513,4 +513,36 @@ l5:
; CHECK: }
}
+; CHECK-LABEL: define void @h_con(i32 %p) {
+define void @h_con(i32 %p) {
+ %x = icmp ult i32 %p, 5
+ br i1 %x, label %l1, label %l2
+
+l1:
+ call void @j()
+ br label %l3
+
+l2:
+ call void @k()
+ br label %l3
+
+l3:
+; CHECK: call void @g() [[CON:#[0-9]+]]
+; CHECK-NOT: call void @g() [[CON]]
+ call void @g() convergent
+ %y = icmp ult i32 %p, 5
+ br i1 %y, label %l4, label %l5
+
+l4:
+ call void @j()
+ ret void
+
+l5:
+ call void @k()
+ ret void
+; CHECK: }
+}
+
+
; CHECK: attributes [[NOD]] = { noduplicate }
+; CHECK: attributes [[CON]] = { convergent }
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