[llvm] r342335 - [InstCombine] Support (sub (sext x), (sext y)) --> (sext (sub x, y)) and (sub (zext x), (zext y)) --> (zext (sub x, y))
Craig Topper via llvm-commits
llvm-commits at lists.llvm.org
Sat Sep 15 11:54:10 PDT 2018
Author: ctopper
Date: Sat Sep 15 11:54:10 2018
New Revision: 342335
URL: http://llvm.org/viewvc/llvm-project?rev=342335&view=rev
Log:
[InstCombine] Support (sub (sext x), (sext y)) --> (sext (sub x, y)) and (sub (zext x), (zext y)) --> (zext (sub x, y))
Summary:
If the sub doesn't overflow in the original type we can move it above the sext/zext.
This is similar to what we do for add. The overflow checking for sub is currently weaker than add, so the test cases are constructed for what is supported.
Reviewers: spatel
Reviewed By: spatel
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D52075
Modified:
llvm/trunk/lib/Transforms/InstCombine/InstCombineAddSub.cpp
llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp
llvm/trunk/test/Transforms/InstCombine/narrow-math.ll
Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineAddSub.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineAddSub.cpp?rev=342335&r1=342334&r2=342335&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineAddSub.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineAddSub.cpp Sat Sep 15 11:54:10 2018
@@ -1697,6 +1697,9 @@ Instruction *InstCombiner::visitSub(Bina
return SelectInst::Create(Cmp, Neg, A);
}
+ if (Instruction *Ext = narrowMathIfNoOverflow(I))
+ return Ext;
+
bool Changed = false;
if (!I.hasNoSignedWrap() && willNotOverflowSignedSub(Op0, Op1, I)) {
Changed = true;
Modified: llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp?rev=342335&r1=342334&r2=342335&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp Sat Sep 15 11:54:10 2018
@@ -1451,29 +1451,40 @@ Instruction *InstCombiner::foldShuffledB
/// sure the narrow op does not overflow.
Instruction *InstCombiner::narrowMathIfNoOverflow(BinaryOperator &BO) {
// We need at least one extended operand.
- Value *LHS = BO.getOperand(0), *RHS = BO.getOperand(1);
+ Value *Op0 = BO.getOperand(0), *Op1 = BO.getOperand(1);
+
+ // If this is a sub, we swap the operands since we always want an extension
+ // on the RHS. The LHS can be an extension or a constant.
+ if (BO.getOpcode() == Instruction::Sub)
+ std::swap(Op0, Op1);
+
Value *X;
- bool IsSext = match(LHS, m_SExt(m_Value(X)));
- if (!IsSext && !match(LHS, m_ZExt(m_Value(X))))
+ bool IsSext = match(Op0, m_SExt(m_Value(X)));
+ if (!IsSext && !match(Op0, m_ZExt(m_Value(X))))
return nullptr;
// If both operands are the same extension from the same source type and we
// can eliminate at least one (hasOneUse), this might work.
CastInst::CastOps CastOpc = IsSext ? Instruction::SExt : Instruction::ZExt;
Value *Y;
- if (!(match(RHS, m_ZExtOrSExt(m_Value(Y))) && X->getType() == Y->getType() &&
- cast<Operator>(RHS)->getOpcode() == CastOpc &&
- (LHS->hasOneUse() || RHS->hasOneUse()))) {
+ if (!(match(Op1, m_ZExtOrSExt(m_Value(Y))) && X->getType() == Y->getType() &&
+ cast<Operator>(Op1)->getOpcode() == CastOpc &&
+ (Op0->hasOneUse() || Op1->hasOneUse()))) {
// If that did not match, see if we have a suitable constant operand.
// Truncating and extending must produce the same constant.
Constant *WideC;
- if (!LHS->hasOneUse() || !match(RHS, m_Constant(WideC)))
+ if (!Op0->hasOneUse() || !match(Op1, m_Constant(WideC)))
return nullptr;
Constant *NarrowC = ConstantExpr::getTrunc(WideC, X->getType());
if (ConstantExpr::getCast(CastOpc, NarrowC, BO.getType()) != WideC)
return nullptr;
Y = NarrowC;
}
+
+ // Swap back now that we found our operands.
+ if (BO.getOpcode() == Instruction::Sub)
+ std::swap(X, Y);
+
// Both operands have narrow versions. Last step: the math must not overflow
// in the narrow width.
if (!willNotOverflow(BO.getOpcode(), X, Y, BO, IsSext))
Modified: llvm/trunk/test/Transforms/InstCombine/narrow-math.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/narrow-math.ll?rev=342335&r1=342334&r2=342335&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/narrow-math.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/narrow-math.ll Sat Sep 15 11:54:10 2018
@@ -491,5 +491,140 @@ define i64 @test12(i32 %V) {
ret i64 %add
}
+define i64 @test13(i32 %V) {
+; CHECK-LABEL: @test13(
+; CHECK-NEXT: [[CALL1:%.*]] = call i32 @callee(), !range !2
+; CHECK-NEXT: [[CALL2:%.*]] = call i32 @callee(), !range !3
+; CHECK-NEXT: [[SUBCONV:%.*]] = sub nsw i32 [[CALL1]], [[CALL2]]
+; CHECK-NEXT: [[SUB:%.*]] = sext i32 [[SUBCONV]] to i64
+; CHECK-NEXT: ret i64 [[SUB]]
+;
+ %call1 = call i32 @callee(), !range !2
+ %call2 = call i32 @callee(), !range !3
+ %sext1 = sext i32 %call1 to i64
+ %sext2 = sext i32 %call2 to i64
+ %sub = sub i64 %sext1, %sext2
+ ret i64 %sub
+}
+
+define i64 @test14(i32 %V) {
+; CHECK-LABEL: @test14(
+; CHECK-NEXT: [[CALL1:%.*]] = call i32 @callee(), !range !2
+; CHECK-NEXT: [[CALL2:%.*]] = call i32 @callee(), !range !0
+; CHECK-NEXT: [[SUBCONV:%.*]] = sub nuw nsw i32 [[CALL1]], [[CALL2]]
+; CHECK-NEXT: [[SUB:%.*]] = zext i32 [[SUBCONV]] to i64
+; CHECK-NEXT: ret i64 [[SUB]]
+;
+ %call1 = call i32 @callee(), !range !2
+ %call2 = call i32 @callee(), !range !0
+ %zext1 = zext i32 %call1 to i64
+ %zext2 = zext i32 %call2 to i64
+ %sub = sub i64 %zext1, %zext2
+ ret i64 %sub
+}
+
+define i64 @test15(i32 %V) {
+; CHECK-LABEL: @test15(
+; CHECK-NEXT: [[ASHR:%.*]] = ashr i32 [[V:%.*]], 1
+; CHECK-NEXT: [[SUBCONV:%.*]] = sub nsw i32 8, [[ASHR]]
+; CHECK-NEXT: [[SUB:%.*]] = sext i32 [[SUBCONV]] to i64
+; CHECK-NEXT: ret i64 [[SUB]]
+;
+ %ashr = ashr i32 %V, 1
+ %sext = sext i32 %ashr to i64
+ %sub = sub i64 8, %sext
+ ret i64 %sub
+}
+
+define <2 x i64> @test15vec(<2 x i32> %V) {
+; CHECK-LABEL: @test15vec(
+; CHECK-NEXT: [[ASHR:%.*]] = ashr <2 x i32> [[V:%.*]], <i32 1, i32 1>
+; CHECK-NEXT: [[SUBCONV:%.*]] = sub nsw <2 x i32> <i32 8, i32 8>, [[ASHR]]
+; CHECK-NEXT: [[SUB:%.*]] = sext <2 x i32> [[SUBCONV]] to <2 x i64>
+; CHECK-NEXT: ret <2 x i64> [[SUB]]
+;
+ %ashr = ashr <2 x i32> %V, <i32 1, i32 1>
+ %sext = sext <2 x i32> %ashr to <2 x i64>
+ %sub = sub <2 x i64> <i64 8, i64 8>, %sext
+ ret <2 x i64> %sub
+}
+
+define i64 @test16(i32 %V) {
+; CHECK-LABEL: @test16(
+; CHECK-NEXT: [[LSHR:%.*]] = lshr i32 [[V:%.*]], 1
+; CHECK-NEXT: [[SUBCONV:%.*]] = sub nuw i32 -2, [[LSHR]]
+; CHECK-NEXT: [[SUB:%.*]] = zext i32 [[SUBCONV]] to i64
+; CHECK-NEXT: ret i64 [[SUB]]
+;
+ %lshr = lshr i32 %V, 1
+ %zext = zext i32 %lshr to i64
+ %sub = sub i64 4294967294, %zext
+ ret i64 %sub
+}
+
+define <2 x i64> @test16vec(<2 x i32> %V) {
+; CHECK-LABEL: @test16vec(
+; CHECK-NEXT: [[LSHR:%.*]] = lshr <2 x i32> [[V:%.*]], <i32 1, i32 1>
+; CHECK-NEXT: [[SUBCONV:%.*]] = sub nuw <2 x i32> <i32 -2, i32 -2>, [[LSHR]]
+; CHECK-NEXT: [[SUB:%.*]] = zext <2 x i32> [[SUBCONV]] to <2 x i64>
+; CHECK-NEXT: ret <2 x i64> [[SUB]]
+;
+ %lshr = lshr <2 x i32> %V, <i32 1, i32 1>
+ %zext = zext <2 x i32> %lshr to <2 x i64>
+ %sub = sub <2 x i64> <i64 4294967294, i64 4294967294>, %zext
+ ret <2 x i64> %sub
+}
+
+; Negative test. Both have the same range so we can't guarantee the subtract
+; won't wrap.
+define i64 @test17(i32 %V) {
+; CHECK-LABEL: @test17(
+; CHECK-NEXT: [[CALL1:%.*]] = call i32 @callee(), !range !0
+; CHECK-NEXT: [[CALL2:%.*]] = call i32 @callee(), !range !0
+; CHECK-NEXT: [[SEXT1:%.*]] = zext i32 [[CALL1]] to i64
+; CHECK-NEXT: [[SEXT2:%.*]] = zext i32 [[CALL2]] to i64
+; CHECK-NEXT: [[SUB:%.*]] = sub nsw i64 [[SEXT1]], [[SEXT2]]
+; CHECK-NEXT: ret i64 [[SUB]]
+;
+ %call1 = call i32 @callee(), !range !0
+ %call2 = call i32 @callee(), !range !0
+ %sext1 = zext i32 %call1 to i64
+ %sext2 = zext i32 %call2 to i64
+ %sub = sub i64 %sext1, %sext2
+ ret i64 %sub
+}
+
+; Negative test. LHS is large positive 32-bit number. Range of callee can
+; cause overflow.
+define i64 @test18(i32 %V) {
+; CHECK-LABEL: @test18(
+; CHECK-NEXT: [[CALL1:%.*]] = call i32 @callee(), !range !1
+; CHECK-NEXT: [[SEXT1:%.*]] = sext i32 [[CALL1]] to i64
+; CHECK-NEXT: [[SUB:%.*]] = sub nsw i64 2147481648, [[SEXT1]]
+; CHECK-NEXT: ret i64 [[SUB]]
+;
+ %call1 = call i32 @callee(), !range !1
+ %sext1 = sext i32 %call1 to i64
+ %sub = sub i64 2147481648, %sext1
+ ret i64 %sub
+}
+
+; Negative test. LHS is large negative 32-bit number. Range of callee can
+; cause overflow.
+define i64 @test19(i32 %V) {
+; CHECK-LABEL: @test19(
+; CHECK-NEXT: [[CALL1:%.*]] = call i32 @callee(), !range !0
+; CHECK-NEXT: [[TMP1:%.*]] = zext i32 [[CALL1]] to i64
+; CHECK-NEXT: [[SUB:%.*]] = sub nuw nsw i64 -2147481648, [[TMP1]]
+; CHECK-NEXT: ret i64 [[SUB]]
+;
+ %call1 = call i32 @callee(), !range !0
+ %sext1 = sext i32 %call1 to i64
+ %sub = sub i64 -2147481648, %sext1
+ ret i64 %sub
+}
+
!0 = !{ i32 0, i32 2000 }
!1 = !{ i32 -2000, i32 0 }
+!2 = !{ i32 -512, i32 -255 }
+!3 = !{ i32 -128, i32 0 }
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