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-rw-r--r--llvm/lib/Transforms/Scalar/IndVarSimplify.cpp161
-rw-r--r--llvm/test/Transforms/IndVarSimplify/2009-04-14-shorten_iv_vars.ll114
2 files changed, 235 insertions, 40 deletions
diff --git a/llvm/lib/Transforms/Scalar/IndVarSimplify.cpp b/llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
index 205efca6ce2..20d389b1bf8 100644
--- a/llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
+++ b/llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
@@ -467,8 +467,12 @@ static const Type *getEffectiveIndvarType(const PHINode *Phi) {
/// whether an induction variable in the same type that starts
/// at 0 would undergo signed overflow.
///
-/// In addition to setting the NoSignedWrap, and NoUnsignedWrap,
-/// variables, return the PHI for this induction variable.
+/// In addition to setting the NoSignedWrap and NoUnsignedWrap
+/// variables to true when appropriate (they are not set to false here),
+/// return the PHI for this induction variable. Also record the initial
+/// and final values and the increment; these are not meaningful unless
+/// either NoSignedWrap or NoUnsignedWrap is true, and are always meaningful
+/// in that case, although the final value may be 0 indicating a nonconstant.
///
/// TODO: This duplicates a fair amount of ScalarEvolution logic.
/// Perhaps this can be merged with
@@ -479,7 +483,10 @@ static const PHINode *TestOrigIVForWrap(const Loop *L,
const BranchInst *BI,
const Instruction *OrigCond,
bool &NoSignedWrap,
- bool &NoUnsignedWrap) {
+ bool &NoUnsignedWrap,
+ const ConstantInt* &InitialVal,
+ const ConstantInt* &IncrVal,
+ const ConstantInt* &LimitVal) {
// Verify that the loop is sane and find the exit condition.
const ICmpInst *Cmp = dyn_cast<ICmpInst>(OrigCond);
if (!Cmp) return 0;
@@ -542,31 +549,31 @@ static const PHINode *TestOrigIVForWrap(const Loop *L,
// Get the increment instruction. Look past casts if we will
// be able to prove that the original induction variable doesn't
// undergo signed or unsigned overflow, respectively.
- const Value *IncrVal = CmpLHS;
+ const Value *IncrInst = CmpLHS;
if (isSigned) {
if (const SExtInst *SI = dyn_cast<SExtInst>(CmpLHS)) {
if (!isa<ConstantInt>(CmpRHS) ||
!cast<ConstantInt>(CmpRHS)->getValue()
- .isSignedIntN(IncrVal->getType()->getPrimitiveSizeInBits()))
+ .isSignedIntN(IncrInst->getType()->getPrimitiveSizeInBits()))
return 0;
- IncrVal = SI->getOperand(0);
+ IncrInst = SI->getOperand(0);
}
} else {
if (const ZExtInst *ZI = dyn_cast<ZExtInst>(CmpLHS)) {
if (!isa<ConstantInt>(CmpRHS) ||
!cast<ConstantInt>(CmpRHS)->getValue()
- .isIntN(IncrVal->getType()->getPrimitiveSizeInBits()))
+ .isIntN(IncrInst->getType()->getPrimitiveSizeInBits()))
return 0;
- IncrVal = ZI->getOperand(0);
+ IncrInst = ZI->getOperand(0);
}
}
// For now, only analyze induction variables that have simple increments.
- const BinaryOperator *IncrOp = dyn_cast<BinaryOperator>(IncrVal);
- if (!IncrOp ||
- IncrOp->getOpcode() != Instruction::Add ||
- !isa<ConstantInt>(IncrOp->getOperand(1)) ||
- !cast<ConstantInt>(IncrOp->getOperand(1))->equalsInt(1))
+ const BinaryOperator *IncrOp = dyn_cast<BinaryOperator>(IncrInst);
+ if (!IncrOp || IncrOp->getOpcode() != Instruction::Add)
+ return 0;
+ IncrVal = dyn_cast<ConstantInt>(IncrOp->getOperand(1));
+ if (!IncrVal)
return 0;
// Make sure the PHI looks like a normal IV.
@@ -584,21 +591,78 @@ static const PHINode *TestOrigIVForWrap(const Loop *L,
// For now, only analyze loops with a constant start value, so that
// we can easily determine if the start value is not a maximum value
// which would wrap on the first iteration.
- const ConstantInt *InitialVal =
- dyn_cast<ConstantInt>(PN->getIncomingValue(IncomingEdge));
+ InitialVal = dyn_cast<ConstantInt>(PN->getIncomingValue(IncomingEdge));
if (!InitialVal)
return 0;
- // The original induction variable will start at some non-max value,
- // it counts up by one, and the loop iterates only while it remans
- // less than some value in the same type. As such, it will never wrap.
+ // The upper limit need not be a constant; we'll check later.
+ LimitVal = dyn_cast<ConstantInt>(CmpRHS);
+
+ // We detect the impossibility of wrapping in two cases, both of
+ // which require starting with a non-max value:
+ // - The IV counts up by one, and the loop iterates only while it remains
+ // less than a limiting value (any) in the same type.
+ // - The IV counts up by a positive increment other than 1, and the
+ // constant limiting value + the increment is less than the max value
+ // (computed as max-increment to avoid overflow)
if (isSigned && !InitialVal->getValue().isMaxSignedValue()) {
- NoSignedWrap = true;
- } else if (!isSigned && !InitialVal->getValue().isMaxValue())
- NoUnsignedWrap = true;
+ if (IncrVal->equalsInt(1))
+ NoSignedWrap = true; // LimitVal need not be constant
+ else if (LimitVal) {
+ uint64_t numBits = LimitVal->getValue().getBitWidth();
+ if (IncrVal->getValue().sgt(APInt::getNullValue(numBits)) &&
+ (APInt::getSignedMaxValue(numBits) - IncrVal->getValue())
+ .sgt(LimitVal->getValue()))
+ NoSignedWrap = true;
+ }
+ } else if (!isSigned && !InitialVal->getValue().isMaxValue()) {
+ if (IncrVal->equalsInt(1))
+ NoUnsignedWrap = true; // LimitVal need not be constant
+ else if (LimitVal) {
+ uint64_t numBits = LimitVal->getValue().getBitWidth();
+ if (IncrVal->getValue().ugt(APInt::getNullValue(numBits)) &&
+ (APInt::getMaxValue(numBits) - IncrVal->getValue())
+ .ugt(LimitVal->getValue()))
+ NoUnsignedWrap = true;
+ }
+ }
return PN;
}
+static Value *getSignExtendedTruncVar(const SCEVAddRecExpr *AR,
+ ScalarEvolution *SE,
+ const Type *LargestType, Loop *L,
+ const Type *myType,
+ SCEVExpander &Rewriter,
+ BasicBlock::iterator InsertPt) {
+ SCEVHandle ExtendedStart =
+ SE->getSignExtendExpr(AR->getStart(), LargestType);
+ SCEVHandle ExtendedStep =
+ SE->getSignExtendExpr(AR->getStepRecurrence(*SE), LargestType);
+ SCEVHandle ExtendedAddRec =
+ SE->getAddRecExpr(ExtendedStart, ExtendedStep, L);
+ if (LargestType != myType)
+ ExtendedAddRec = SE->getTruncateExpr(ExtendedAddRec, myType);
+ return Rewriter.expandCodeFor(ExtendedAddRec, InsertPt);
+}
+
+static Value *getZeroExtendedTruncVar(const SCEVAddRecExpr *AR,
+ ScalarEvolution *SE,
+ const Type *LargestType, Loop *L,
+ const Type *myType,
+ SCEVExpander &Rewriter,
+ BasicBlock::iterator InsertPt) {
+ SCEVHandle ExtendedStart =
+ SE->getZeroExtendExpr(AR->getStart(), LargestType);
+ SCEVHandle ExtendedStep =
+ SE->getZeroExtendExpr(AR->getStepRecurrence(*SE), LargestType);
+ SCEVHandle ExtendedAddRec =
+ SE->getAddRecExpr(ExtendedStart, ExtendedStep, L);
+ if (LargestType != myType)
+ ExtendedAddRec = SE->getTruncateExpr(ExtendedAddRec, myType);
+ return Rewriter.expandCodeFor(ExtendedAddRec, InsertPt);
+}
+
bool IndVarSimplify::runOnLoop(Loop *L, LPPassManager &LPM) {
LI = &getAnalysis<LoopInfo>();
SE = &getAnalysis<ScalarEvolution>();
@@ -680,6 +744,7 @@ bool IndVarSimplify::runOnLoop(Loop *L, LPPassManager &LPM) {
// using it. We can currently only handle loops with a single exit.
bool NoSignedWrap = false;
bool NoUnsignedWrap = false;
+ const ConstantInt* InitialVal, * IncrVal, * LimitVal;
const PHINode *OrigControllingPHI = 0;
if (!isa<SCEVCouldNotCompute>(BackedgeTakenCount) && ExitingBlock)
// Can't rewrite non-branch yet.
@@ -688,7 +753,8 @@ bool IndVarSimplify::runOnLoop(Loop *L, LPPassManager &LPM) {
// Determine if the OrigIV will ever undergo overflow.
OrigControllingPHI =
TestOrigIVForWrap(L, BI, OrigCond,
- NoSignedWrap, NoUnsignedWrap);
+ NoSignedWrap, NoUnsignedWrap,
+ InitialVal, IncrVal, LimitVal);
// We'll be replacing the original condition, so it'll be dead.
DeadInsts.insert(OrigCond);
@@ -733,29 +799,44 @@ bool IndVarSimplify::runOnLoop(Loop *L, LPPassManager &LPM) {
for (Value::use_iterator UI = PN->use_begin(), UE = PN->use_end();
UI != UE; ++UI) {
if (isa<SExtInst>(UI) && NoSignedWrap) {
- SCEVHandle ExtendedStart =
- SE->getSignExtendExpr(AR->getStart(), LargestType);
- SCEVHandle ExtendedStep =
- SE->getSignExtendExpr(AR->getStepRecurrence(*SE), LargestType);
- SCEVHandle ExtendedAddRec =
- SE->getAddRecExpr(ExtendedStart, ExtendedStep, L);
- if (LargestType != UI->getType())
- ExtendedAddRec = SE->getTruncateExpr(ExtendedAddRec, UI->getType());
- Value *TruncIndVar = Rewriter.expandCodeFor(ExtendedAddRec, InsertPt);
+ Value *TruncIndVar = getSignExtendedTruncVar(AR, SE, LargestType, L,
+ UI->getType(), Rewriter, InsertPt);
UI->replaceAllUsesWith(TruncIndVar);
if (Instruction *DeadUse = dyn_cast<Instruction>(*UI))
DeadInsts.insert(DeadUse);
}
+ // See if we can figure out sext(i+constant) doesn't wrap, so we can
+ // use a larger add. This is common in subscripting.
+ Instruction *UInst = dyn_cast<Instruction>(*UI);
+ if (UInst && UInst->getOpcode()==Instruction::Add &&
+ UInst->hasOneUse() &&
+ isa<ConstantInt>(UInst->getOperand(1)) &&
+ isa<SExtInst>(UInst->use_begin()) && NoSignedWrap && LimitVal) {
+ uint64_t numBits = LimitVal->getValue().getBitWidth();
+ ConstantInt* RHS = dyn_cast<ConstantInt>(UInst->getOperand(1));
+ if (((APInt::getSignedMaxValue(numBits) - IncrVal->getValue()) -
+ RHS->getValue()).sgt(LimitVal->getValue())) {
+ SExtInst* oldSext = dyn_cast<SExtInst>(UInst->use_begin());
+ Value *TruncIndVar = getSignExtendedTruncVar(AR, SE, LargestType, L,
+ oldSext->getType(), Rewriter,
+ InsertPt);
+ APInt APcopy = APInt(RHS->getValue());
+ ConstantInt* newRHS =
+ ConstantInt::get(APcopy.sext(oldSext->getType()->
+ getPrimitiveSizeInBits()));
+ Value *NewAdd = BinaryOperator::CreateAdd(TruncIndVar, newRHS,
+ UInst->getName()+".nosex",
+ UInst);
+ oldSext->replaceAllUsesWith(NewAdd);
+ if (Instruction *DeadUse = dyn_cast<Instruction>(oldSext))
+ DeadInsts.insert(DeadUse);
+ if (Instruction *DeadUse = dyn_cast<Instruction>(UInst))
+ DeadInsts.insert(DeadUse);
+ }
+ }
if (isa<ZExtInst>(UI) && NoUnsignedWrap) {
- SCEVHandle ExtendedStart =
- SE->getZeroExtendExpr(AR->getStart(), LargestType);
- SCEVHandle ExtendedStep =
- SE->getZeroExtendExpr(AR->getStepRecurrence(*SE), LargestType);
- SCEVHandle ExtendedAddRec =
- SE->getAddRecExpr(ExtendedStart, ExtendedStep, L);
- if (LargestType != UI->getType())
- ExtendedAddRec = SE->getTruncateExpr(ExtendedAddRec, UI->getType());
- Value *TruncIndVar = Rewriter.expandCodeFor(ExtendedAddRec, InsertPt);
+ Value *TruncIndVar = getZeroExtendedTruncVar(AR, SE, LargestType, L,
+ UI->getType(), Rewriter, InsertPt);
UI->replaceAllUsesWith(TruncIndVar);
if (Instruction *DeadUse = dyn_cast<Instruction>(*UI))
DeadInsts.insert(DeadUse);
diff --git a/llvm/test/Transforms/IndVarSimplify/2009-04-14-shorten_iv_vars.ll b/llvm/test/Transforms/IndVarSimplify/2009-04-14-shorten_iv_vars.ll
new file mode 100644
index 00000000000..134c9c74d3a
--- /dev/null
+++ b/llvm/test/Transforms/IndVarSimplify/2009-04-14-shorten_iv_vars.ll
@@ -0,0 +1,114 @@
+; RUN: llvm-as < %s | opt -indvars | llvm-dis | not grep {sext}
+; ModuleID = '<stdin>'
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128"
+target triple = "x86_64-apple-darwin9.6"
+@a = external global i32* ; <i32**> [#uses=3]
+@b = external global i32* ; <i32**> [#uses=3]
+@c = external global i32* ; <i32**> [#uses=3]
+@d = external global i32* ; <i32**> [#uses=3]
+@e = external global i32* ; <i32**> [#uses=3]
+@f = external global i32* ; <i32**> [#uses=3]
+
+define void @foo() nounwind {
+bb1.thread:
+ br label %bb1
+
+bb1: ; preds = %bb1, %bb1.thread
+ %i.0.reg2mem.0 = phi i32 [ 0, %bb1.thread ], [ %84, %bb1 ] ; <i32> [#uses=19]
+ %0 = load i32** @a, align 8 ; <i32*> [#uses=1]
+ %1 = load i32** @b, align 8 ; <i32*> [#uses=1]
+ %2 = sext i32 %i.0.reg2mem.0 to i64 ; <i64> [#uses=1]
+ %3 = getelementptr i32* %1, i64 %2 ; <i32*> [#uses=1]
+ %4 = load i32* %3, align 1 ; <i32> [#uses=1]
+ %5 = load i32** @c, align 8 ; <i32*> [#uses=1]
+ %6 = sext i32 %i.0.reg2mem.0 to i64 ; <i64> [#uses=1]
+ %7 = getelementptr i32* %5, i64 %6 ; <i32*> [#uses=1]
+ %8 = load i32* %7, align 1 ; <i32> [#uses=1]
+ %9 = add i32 %8, %4 ; <i32> [#uses=1]
+ %10 = sext i32 %i.0.reg2mem.0 to i64 ; <i64> [#uses=1]
+ %11 = getelementptr i32* %0, i64 %10 ; <i32*> [#uses=1]
+ store i32 %9, i32* %11, align 1
+ %12 = load i32** @a, align 8 ; <i32*> [#uses=1]
+ %13 = add i32 %i.0.reg2mem.0, 1 ; <i32> [#uses=1]
+ %14 = load i32** @b, align 8 ; <i32*> [#uses=1]
+ %15 = add i32 %i.0.reg2mem.0, 1 ; <i32> [#uses=1]
+ %16 = sext i32 %15 to i64 ; <i64> [#uses=1]
+ %17 = getelementptr i32* %14, i64 %16 ; <i32*> [#uses=1]
+ %18 = load i32* %17, align 1 ; <i32> [#uses=1]
+ %19 = load i32** @c, align 8 ; <i32*> [#uses=1]
+ %20 = add i32 %i.0.reg2mem.0, 1 ; <i32> [#uses=1]
+ %21 = sext i32 %20 to i64 ; <i64> [#uses=1]
+ %22 = getelementptr i32* %19, i64 %21 ; <i32*> [#uses=1]
+ %23 = load i32* %22, align 1 ; <i32> [#uses=1]
+ %24 = add i32 %23, %18 ; <i32> [#uses=1]
+ %25 = sext i32 %13 to i64 ; <i64> [#uses=1]
+ %26 = getelementptr i32* %12, i64 %25 ; <i32*> [#uses=1]
+ store i32 %24, i32* %26, align 1
+ %27 = load i32** @a, align 8 ; <i32*> [#uses=1]
+ %28 = add i32 %i.0.reg2mem.0, 2 ; <i32> [#uses=1]
+ %29 = load i32** @b, align 8 ; <i32*> [#uses=1]
+ %30 = add i32 %i.0.reg2mem.0, 2 ; <i32> [#uses=1]
+ %31 = sext i32 %30 to i64 ; <i64> [#uses=1]
+ %32 = getelementptr i32* %29, i64 %31 ; <i32*> [#uses=1]
+ %33 = load i32* %32, align 1 ; <i32> [#uses=1]
+ %34 = load i32** @c, align 8 ; <i32*> [#uses=1]
+ %35 = add i32 %i.0.reg2mem.0, 2 ; <i32> [#uses=1]
+ %36 = sext i32 %35 to i64 ; <i64> [#uses=1]
+ %37 = getelementptr i32* %34, i64 %36 ; <i32*> [#uses=1]
+ %38 = load i32* %37, align 1 ; <i32> [#uses=1]
+ %39 = add i32 %38, %33 ; <i32> [#uses=1]
+ %40 = sext i32 %28 to i64 ; <i64> [#uses=1]
+ %41 = getelementptr i32* %27, i64 %40 ; <i32*> [#uses=1]
+ store i32 %39, i32* %41, align 1
+ %42 = load i32** @d, align 8 ; <i32*> [#uses=1]
+ %43 = load i32** @e, align 8 ; <i32*> [#uses=1]
+ %44 = sext i32 %i.0.reg2mem.0 to i64 ; <i64> [#uses=1]
+ %45 = getelementptr i32* %43, i64 %44 ; <i32*> [#uses=1]
+ %46 = load i32* %45, align 1 ; <i32> [#uses=1]
+ %47 = load i32** @f, align 8 ; <i32*> [#uses=1]
+ %48 = sext i32 %i.0.reg2mem.0 to i64 ; <i64> [#uses=1]
+ %49 = getelementptr i32* %47, i64 %48 ; <i32*> [#uses=1]
+ %50 = load i32* %49, align 1 ; <i32> [#uses=1]
+ %51 = add i32 %50, %46 ; <i32> [#uses=1]
+ %52 = sext i32 %i.0.reg2mem.0 to i64 ; <i64> [#uses=1]
+ %53 = getelementptr i32* %42, i64 %52 ; <i32*> [#uses=1]
+ store i32 %51, i32* %53, align 1
+ %54 = load i32** @d, align 8 ; <i32*> [#uses=1]
+ %55 = add i32 %i.0.reg2mem.0, 1 ; <i32> [#uses=1]
+ %56 = load i32** @e, align 8 ; <i32*> [#uses=1]
+ %57 = add i32 %i.0.reg2mem.0, 1 ; <i32> [#uses=1]
+ %58 = sext i32 %57 to i64 ; <i64> [#uses=1]
+ %59 = getelementptr i32* %56, i64 %58 ; <i32*> [#uses=1]
+ %60 = load i32* %59, align 1 ; <i32> [#uses=1]
+ %61 = load i32** @f, align 8 ; <i32*> [#uses=1]
+ %62 = add i32 %i.0.reg2mem.0, 1 ; <i32> [#uses=1]
+ %63 = sext i32 %62 to i64 ; <i64> [#uses=1]
+ %64 = getelementptr i32* %61, i64 %63 ; <i32*> [#uses=1]
+ %65 = load i32* %64, align 1 ; <i32> [#uses=1]
+ %66 = add i32 %65, %60 ; <i32> [#uses=1]
+ %67 = sext i32 %55 to i64 ; <i64> [#uses=1]
+ %68 = getelementptr i32* %54, i64 %67 ; <i32*> [#uses=1]
+ store i32 %66, i32* %68, align 1
+ %69 = load i32** @d, align 8 ; <i32*> [#uses=1]
+ %70 = add i32 %i.0.reg2mem.0, 2 ; <i32> [#uses=1]
+ %71 = load i32** @e, align 8 ; <i32*> [#uses=1]
+ %72 = add i32 %i.0.reg2mem.0, 2 ; <i32> [#uses=1]
+ %73 = sext i32 %72 to i64 ; <i64> [#uses=1]
+ %74 = getelementptr i32* %71, i64 %73 ; <i32*> [#uses=1]
+ %75 = load i32* %74, align 1 ; <i32> [#uses=1]
+ %76 = load i32** @f, align 8 ; <i32*> [#uses=1]
+ %77 = add i32 %i.0.reg2mem.0, 2 ; <i32> [#uses=1]
+ %78 = sext i32 %77 to i64 ; <i64> [#uses=1]
+ %79 = getelementptr i32* %76, i64 %78 ; <i32*> [#uses=1]
+ %80 = load i32* %79, align 1 ; <i32> [#uses=1]
+ %81 = add i32 %80, %75 ; <i32> [#uses=1]
+ %82 = sext i32 %70 to i64 ; <i64> [#uses=1]
+ %83 = getelementptr i32* %69, i64 %82 ; <i32*> [#uses=1]
+ store i32 %81, i32* %83, align 1
+ %84 = add i32 %i.0.reg2mem.0, 1 ; <i32> [#uses=2]
+ %85 = icmp sgt i32 %84, 23646 ; <i1> [#uses=1]
+ br i1 %85, label %return, label %bb1
+
+return: ; preds = %bb1
+ ret void
+}
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