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Teach CorrelatedValuePropagation to mark adds as no wrap

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Use LVI to prove that adds do not wrap. The change is motivated by https://llvm.org/bugs/show_bug.cgi?id=28620 bug and it's the first step to fix that problem.

Reviewed By: sanjoy

Differential Revision: http://reviews.llvm.org/D23059


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@277592 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Artur Pilipenko 2016-08-03 13:11:39 +00:00
parent 48f2d1dea0
commit 5267dec504
2 changed files with 148 additions and 0 deletions
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57
lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
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@ -18,6 +18,7 @@
#include "llvm/Analysis/InstructionSimplify.h" #include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/LazyValueInfo.h" #include "llvm/Analysis/LazyValueInfo.h"
#include "llvm/IR/CFG.h" #include "llvm/IR/CFG.h"
#include "llvm/IR/ConstantRange.h"
#include "llvm/IR/Constants.h" #include "llvm/IR/Constants.h"
#include "llvm/IR/Function.h" #include "llvm/IR/Function.h"
#include "llvm/IR/Instructions.h" #include "llvm/IR/Instructions.h"
@ -381,6 +382,59 @@ static bool processSDiv(BinaryOperator *SDI, LazyValueInfo *LVI) {
return true; return true;
} }
static bool processAdd(BinaryOperator *AddOp, LazyValueInfo *LVI) {
typedef OverflowingBinaryOperator OBO;
if (AddOp->getType()->isVectorTy() || hasLocalDefs(AddOp))
return false;
bool NSW = AddOp->hasNoSignedWrap();
bool NUW = AddOp->hasNoUnsignedWrap();
if (NSW && NUW)
return false;
BasicBlock *BB = AddOp->getParent();
Value *LHS = AddOp->getOperand(0);
Value *RHS = AddOp->getOperand(1);
ConstantRange LRange = LVI->getConstantRange(LHS, BB, AddOp);
// Initialize RRange only if we need it. If we know that guaranteed no wrap
// range for the given LHS range is empty don't spend time calculating the
// range for the RHS.
Optional<ConstantRange> RRange;
auto LazyRRange = [&] () {
if (!RRange)
RRange = LVI->getConstantRange(RHS, BB, AddOp);
return RRange.getValue();
};
bool Changed = false;
if (!NUW) {
ConstantRange NUWRange =
LRange.makeGuaranteedNoWrapRegion(BinaryOperator::Add, LRange,
OBO::NoUnsignedWrap);
if (!NUWRange.isEmptySet()) {
bool NewNUW = NUWRange.contains(LazyRRange());
AddOp->setHasNoUnsignedWrap(NewNUW);
Changed |= NewNUW;
}
}
if (!NSW) {
ConstantRange NSWRange =
LRange.makeGuaranteedNoWrapRegion(BinaryOperator::Add, LRange,
OBO::NoSignedWrap);
if (!NSWRange.isEmptySet()) {
bool NewNSW = NSWRange.contains(LazyRRange());
AddOp->setHasNoSignedWrap(NewNSW);
Changed |= NewNSW;
}
}
return Changed;
}
static Constant *getConstantAt(Value *V, Instruction *At, LazyValueInfo *LVI) { static Constant *getConstantAt(Value *V, Instruction *At, LazyValueInfo *LVI) {
if (Constant *C = LVI->getConstant(V, At->getParent(), At)) if (Constant *C = LVI->getConstant(V, At->getParent(), At))
return C; return C;
@ -436,6 +490,9 @@ static bool runImpl(Function &F, LazyValueInfo *LVI) {
case Instruction::SDiv: case Instruction::SDiv:
BBChanged |= processSDiv(cast<BinaryOperator>(II), LVI); BBChanged |= processSDiv(cast<BinaryOperator>(II), LVI);
break; break;
case Instruction::Add:
BBChanged |= processAdd(cast<BinaryOperator>(II), LVI);
break;
} }
} }

91
test/Transforms/CorrelatedValuePropagation/add.ll Normal file
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@ -0,0 +1,91 @@
; RUN: opt < %s -correlated-propagation -S | FileCheck %s
; CHECK-LABEL: @test0(
define void @test0(i32 %a) {
entry:
%cmp = icmp slt i32 %a, 100
br i1 %cmp, label %bb, label %exit
bb:
; CHECK: %add = add nsw i32 %a, 1
%add = add i32 %a, 1
br label %exit
exit:
ret void
}
; CHECK-LABEL: @test1(
define void @test1(i32 %a) {
entry:
%cmp = icmp ult i32 %a, 100
br i1 %cmp, label %bb, label %exit
bb:
; CHECK: %add = add nuw nsw i32 %a, 1
%add = add i32 %a, 1
br label %exit
exit:
ret void
}
; CHECK-LABEL: @test2(
define void @test2(i32 %a) {
entry:
%cmp = icmp ult i32 %a, -1
br i1 %cmp, label %bb, label %exit
bb:
; CHECK: %add = add nuw i32 %a, 1
%add = add i32 %a, 1
br label %exit
exit:
ret void
}
; CHECK-LABEL: @test3(
define void @test3(i32 %a) {
entry:
%cmp = icmp ule i32 %a, -1
br i1 %cmp, label %bb, label %exit
bb:
; CHECK: %add = add i32 %a, 1
%add = add i32 %a, 1
br label %exit
exit:
ret void
}
; CHECK-LABEL: @test4(
define void @test4(i32 %a) {
entry:
%cmp = icmp slt i32 %a, 2147483647
br i1 %cmp, label %bb, label %exit
bb:
; CHECK: %add = add nsw i32 %a, 1
%add = add i32 %a, 1
br label %exit
exit:
ret void
}
; CHECK-LABEL: @test5(
define void @test5(i32 %a) {
entry:
%cmp = icmp sle i32 %a, 2147483647
br i1 %cmp, label %bb, label %exit
bb:
; CHECK: %add = add i32 %a, 1
%add = add i32 %a, 1
br label %exit
exit:
ret void
}