[llvm-commits] [llvm] r113025 - in /llvm/trunk: lib/Transforms/Scalar/CorrelatedValuePropagation.cpp test/Transforms/CorrelatedValuePropagation/basic.ll
Owen Anderson
resistor at mac.com
Fri Sep 3 15:47:08 PDT 2010
Author: resistor
Date: Fri Sep 3 17:47:08 2010
New Revision: 113025
URL: http://llvm.org/viewvc/llvm-project?rev=113025&view=rev
Log:
Propagate non-local comparisons. Fixes PR1757.
Modified:
llvm/trunk/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
llvm/trunk/test/Transforms/CorrelatedValuePropagation/basic.ll
Modified: llvm/trunk/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp?rev=113025&r1=113024&r2=113025&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp Fri Sep 3 17:47:08 2010
@@ -17,6 +17,7 @@
#include "llvm/Instructions.h"
#include "llvm/Pass.h"
#include "llvm/Analysis/LazyValueInfo.h"
+#include "llvm/Support/CFG.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/ADT/Statistic.h"
using namespace llvm;
@@ -24,6 +25,7 @@
STATISTIC(NumPhis, "Number of phis propagated");
STATISTIC(NumSelects, "Number of selects propagated");
STATISTIC(NumMemAccess, "Number of memory access targets propagated");
+STATISTIC(NumCmps, "Number of comparisons propagated");
namespace {
class CorrelatedValuePropagation : public FunctionPass {
@@ -32,6 +34,7 @@
bool processSelect(SelectInst *SI);
bool processPHI(PHINode *P);
bool processMemAccess(Instruction *I);
+ bool processCmp(CmpInst *C);
public:
static char ID;
@@ -117,6 +120,47 @@
return true;
}
+/// processCmp - If the value of this comparison could be determined locally,
+/// constant propagation would already have figured it out. Instead, walk
+/// the predecessors and statically evaluate the comparison based on information
+/// available on that edge. If a given static evaluation is true on ALL
+/// incoming edges, then it's true universally and we can simplify the compare.
+bool CorrelatedValuePropagation::processCmp(CmpInst *C) {
+ Value *Op0 = C->getOperand(0);
+ if (isa<Instruction>(Op0) &&
+ cast<Instruction>(Op0)->getParent() == C->getParent())
+ return false;
+
+ Constant *Op1 = dyn_cast<Constant>(C->getOperand(1));
+ if (!Op1) return false;
+
+ pred_iterator PI = pred_begin(C->getParent()), PE = pred_end(C->getParent());
+ if (PI == PE) return false;
+
+ LazyValueInfo::Tristate Result = LVI->getPredicateOnEdge(C->getPredicate(),
+ C->getOperand(0), Op1, *PI, C->getParent());
+ if (Result == LazyValueInfo::Unknown) return false;
+
+ ++PI;
+ while (PI != PE) {
+ LazyValueInfo::Tristate Res = LVI->getPredicateOnEdge(C->getPredicate(),
+ C->getOperand(0), Op1, *PI, C->getParent());
+ if (Res != Result) return false;
+ ++PI;
+ }
+
+ ++NumCmps;
+
+ if (Result == LazyValueInfo::True)
+ C->replaceAllUsesWith(ConstantInt::getTrue(C->getContext()));
+ else
+ C->replaceAllUsesWith(ConstantInt::getFalse(C->getContext()));
+
+ C->eraseFromParent();
+
+ return true;
+}
+
bool CorrelatedValuePropagation::runOnFunction(Function &F) {
LVI = &getAnalysis<LazyValueInfo>();
@@ -133,6 +177,10 @@
case Instruction::PHI:
BBChanged |= processPHI(cast<PHINode>(II));
break;
+ case Instruction::ICmp:
+ case Instruction::FCmp:
+ BBChanged |= processCmp(cast<CmpInst>(II));
+ break;
case Instruction::Load:
case Instruction::Store:
BBChanged |= processMemAccess(II);
Modified: llvm/trunk/test/Transforms/CorrelatedValuePropagation/basic.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/CorrelatedValuePropagation/basic.ll?rev=113025&r1=113024&r2=113025&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/CorrelatedValuePropagation/basic.ll (original)
+++ llvm/trunk/test/Transforms/CorrelatedValuePropagation/basic.ll Fri Sep 3 17:47:08 2010
@@ -56,4 +56,28 @@
%should_be_const = load i8* %a
; CHECK: ret i8 7
ret i8 %should_be_const
+}
+
+; PR1757
+; CHECK: @test4
+define i32 @test4(i32) {
+EntryBlock:
+; CHECK: icmp sgt i32 %0, 2
+ %.demorgan = icmp sgt i32 %0, 2
+ br i1 %.demorgan, label %GreaterThanTwo, label %LessThanOrEqualToTwo
+
+GreaterThanTwo:
+; CHECK-NOT: icmp eq i32 %0, 2
+ icmp eq i32 %0, 2
+; CHECK: br i1 false
+ br i1 %1, label %Impossible, label %NotTwoAndGreaterThanTwo
+
+NotTwoAndGreaterThanTwo:
+ ret i32 2
+
+Impossible:
+ ret i32 1
+
+LessThanOrEqualToTwo:
+ ret i32 0
}
\ No newline at end of file
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