[CVP] Remove some {s|u}sub.with.overflow checks.

This uses ConstantRange::makeGuaranteedNoWrapRegion's newly-added handling for subtraction to allow CVP to remove some subtraction overflow checks. Differential Revision: https://reviews.llvm.org/D40039 llvm-svn: 319807
llvm · Dec 5, 2017 · ea0bafd · ea0bafd
1 parent c32b0fc
commit ea0bafd
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Showing 2 changed files with 23 additions and 15 deletions.
diff --git a/llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp b/llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
@@ -329,25 +329,29 @@ static bool processSwitch(SwitchInst *SI, LazyValueInfo *LVI) {
 // See if we can prove that the given overflow intrinsic will not overflow.
 static bool willNotOverflow(IntrinsicInst *II, LazyValueInfo *LVI) {
  using OBO = OverflowingBinaryOperator;
- auto NoWrapOnAddition = [&] (Value *LHS, Value *RHS, unsigned NoWrapKind) {
+ auto NoWrap = [&] (Instruction::BinaryOps BinOp, unsigned NoWrapKind) {
+ Value *RHS = II->getOperand(1);
  ConstantRange RRange = LVI->getConstantRange(RHS, II->getParent(), II);
  ConstantRange NWRegion = ConstantRange::makeGuaranteedNoWrapRegion(
- BinaryOperator::Add, RRange, NoWrapKind);
+ BinOp, RRange, NoWrapKind);
  // As an optimization, do not compute LRange if we do not need it.
  if (NWRegion.isEmptySet())
  return false;
+ Value *LHS = II->getOperand(0);
  ConstantRange LRange = LVI->getConstantRange(LHS, II->getParent(), II);
  return NWRegion.contains(LRange);
  };
  switch (II->getIntrinsicID()) {
  default:
  break;
  case Intrinsic::uadd_with_overflow:
- return NoWrapOnAddition(II->getOperand(0), II->getOperand(1),
- OBO::NoUnsignedWrap);
+ return NoWrap(Instruction::Add, OBO::NoUnsignedWrap);
  case Intrinsic::sadd_with_overflow:
- return NoWrapOnAddition(II->getOperand(0), II->getOperand(1),
- OBO::NoSignedWrap);
+ return NoWrap(Instruction::Add, OBO::NoSignedWrap);
+ case Intrinsic::usub_with_overflow:
+ return NoWrap(Instruction::Sub, OBO::NoUnsignedWrap);
+ case Intrinsic::ssub_with_overflow:
+ return NoWrap(Instruction::Sub, OBO::NoSignedWrap);
  }
  return false;
 }
@@ -356,12 +360,17 @@ static void processOverflowIntrinsic(IntrinsicInst *II) {
  Value *NewOp = nullptr;
  switch (II->getIntrinsicID()) {
  default:
- llvm_unreachable("Illegal instruction.");
+ llvm_unreachable("Unexpected instruction.");
  case Intrinsic::uadd_with_overflow:
  case Intrinsic::sadd_with_overflow:
  NewOp = BinaryOperator::CreateAdd(II->getOperand(0), II->getOperand(1),
  II->getName(), II);
  break;
+ case Intrinsic::usub_with_overflow:
+ case Intrinsic::ssub_with_overflow:
+ NewOp = BinaryOperator::CreateSub(II->getOperand(0), II->getOperand(1),
+ II->getName(), II);
+ break;
  }
  ++NumOverflows;
  IRBuilder<> B(II);
@@ -376,7 +385,7 @@ static bool processCallSite(CallSite CS, LazyValueInfo *LVI) {
  SmallVector<unsigned, 4> ArgNos;
  unsigned ArgNo = 0;
 
- if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(CS.getInstruction())) {
+ if (auto *II = dyn_cast<IntrinsicInst>(CS.getInstruction())) {
  if (willNotOverflow(II, LVI)) {
  processOverflowIntrinsic(II);
  return true;

diff --git a/llvm/test/Transforms/CorrelatedValuePropagation/overflows.ll b/llvm/test/Transforms/CorrelatedValuePropagation/overflows.ll
@@ -13,8 +13,7 @@ declare void @llvm.trap()
 
 define i32 @signed_add(i32 %x, i32 %y) {
 ; CHECK-LABEL: @signed_add(
-; CHECK: @llvm.ssub.with.overflow.i32
-; CHECK: @llvm.ssub.with.overflow.i32
+; CHECK-NOT: @llvm.ssub.with.overflow.i32
 ; CHECK: @llvm.sadd.with.overflow.i32
 entry:
  %cmp = icmp sgt i32 %y, 0
@@ -61,7 +60,7 @@ cond.end: ; preds = %cond.false, %cont,
 
 define i32 @unsigned_add(i32 %x, i32 %y) {
 ; CHECK-LABEL: @unsigned_add(
-; CHECK: @llvm.usub.with.overflow.i32
+; CHECK-NOT: @llvm.usub.with.overflow.i32
 ; CHECK: @llvm.uadd.with.overflow.i32
 entry:
  %0 = tail call { i32, i1 } @llvm.usub.with.overflow.i32(i32 -1, i32 %y)
@@ -203,7 +202,7 @@ cond.end: ; preds = %cond.false, %entry
 
 define i32 @signed_sub_r1(i32 %x) {
 ; CHECK-LABEL: @signed_sub_r1(
-; CHECK: @llvm.ssub.with.overflow.i32
+; CHECK-NOT: @llvm.ssub.with.overflow.i32
 entry:
  %cmp = icmp eq i32 %x, -2147483648
  br i1 %cmp, label %cond.end, label %cond.false
@@ -225,7 +224,7 @@ cond.end: ; preds = %cond.false, %entry
 
 define i32 @unsigned_sub_r1(i32 %x) {
 ; CHECK-LABEL: @unsigned_sub_r1(
-; CHECK: @llvm.usub.with.overflow.i32
+; CHECK-NOT: @llvm.usub.with.overflow.i32
 entry:
  %cmp = icmp eq i32 %x, 0
  br i1 %cmp, label %cond.end, label %cond.false
@@ -269,7 +268,7 @@ cond.end: ; preds = %cond.false, %entry
 
 define i32 @signed_sub_rn1(i32 %x) {
 ; CHECK-LABEL: @signed_sub_rn1(
-; CHECK: @llvm.ssub.with.overflow.i32
+; CHECK-NOT: @llvm.ssub.with.overflow.i32
 entry:
  %cmp = icmp eq i32 %x, 2147483647
  br i1 %cmp, label %cond.end, label %cond.false
@@ -293,7 +292,7 @@ declare i32 @bar(i32)
 
 define void @unsigned_loop(i32 %i) {
 ; CHECK-LABEL: @unsigned_loop(
-; CHECK: @llvm.usub.with.overflow.i32
+; CHECK-NOT: @llvm.usub.with.overflow.i32
 entry:
  %cmp3 = icmp eq i32 %i, 0
  br i1 %cmp3, label %while.end, label %while.body.preheader