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[instcombine] Fold overflow check using overflow intrinsic to comparison

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This follows up to D104665 (which added umulo handling alongside the existing uaddo case), and generalizes for the remaining overflow intrinsics.

I went to add analogous handling to LVI, and discovered that LVI already had a more general implementation. Instead, we can port was LVI does to instcombine. (For context, LVI uses makeExactNoWrapRegion to constrain the value 'x' in blocks reached after a branch on the condition `op.with.overflow(x, C).overflow`.)

Differential Revision: https://reviews.llvm.org/D104932
This commit is contained in:
Philip Reames 2021-07-01 09:17:04 -07:00
parent 6203a57d08
commit ade0ec7fb0
5 changed files with 56 additions and 80 deletions
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51
lib/Transforms/InstCombine/InstructionCombining.cpp
View File

@ -3089,33 +3089,32 @@ Instruction *InstCombinerImpl::visitExtractValueInst(ExtractValueInst &EV) {
assert(*EV.idx_begin() == 1 &&
"unexpected extract index for overflow inst");
// If the normal result of the computation is dead, and the RHS is a
// constant, we can transform this into a range comparison for many cases.
// TODO: We can generalize these for non-constant rhs when the newly
// formed expressions are known to simplify. Constants are merely one
// such case.
// TODO: Handle vector splats.
switch (WO->getIntrinsicID()) {
default:
break;
case Intrinsic::uadd_with_overflow:
// overflow = uadd a, -4 --> overflow = icmp ugt a, 3
if (ConstantInt *CI = dyn_cast<ConstantInt>(WO->getRHS()))
return new ICmpInst(ICmpInst::ICMP_UGT, WO->getLHS(),
ConstantExpr::getNot(CI));
break;
case Intrinsic::umul_with_overflow:
// overflow for umul a, C --> a > UINT_MAX udiv C
// (unless C == 0, in which case no overflow ever occurs)
if (ConstantInt *CI = dyn_cast<ConstantInt>(WO->getRHS())) {
assert(!CI->isZero() && "handled by instruction simplify");
auto UMax = APInt::getMaxValue(CI->getType()->getBitWidth());
auto *Op =
ConstantExpr::getUDiv(ConstantInt::get(CI->getType(), UMax), CI);
return new ICmpInst(ICmpInst::ICMP_UGT, WO->getLHS(), Op);
// If only the overflow result is used, and the right hand side is a
// constant (or constant splat), we can remove the intrinsic by directly
// checking for overflow.
const APInt *C;
if (match(WO->getRHS(), m_APInt(C))) {
// Compute the no-wrap range [X,Y) for LHS given RHS=C, then
// check for the inverted range using range offset trick (i.e.
// use a subtract to shift the range to bottom of either the
// signed or unsigned domain and then use a single compare to
// check range membership).
ConstantRange NWR =
ConstantRange::makeExactNoWrapRegion(WO->getBinaryOp(), *C,
WO->getNoWrapKind());
APInt Min = WO->isSigned() ? NWR.getSignedMin() : NWR.getUnsignedMin();
NWR = NWR.subtract(Min);
CmpInst::Predicate Pred;
APInt NewRHSC;
if (NWR.getEquivalentICmp(Pred, NewRHSC)) {
auto *OpTy = WO->getRHS()->getType();
auto *NewLHS = Builder.CreateSub(WO->getLHS(),
ConstantInt::get(OpTy, Min));
return new ICmpInst(ICmpInst::getInversePredicate(Pred), NewLHS,
ConstantInt::get(OpTy, NewRHSC));
}
break;
};
}
}
}
if (LoadInst *L = dyn_cast<LoadInst>(Agg))

21
test/Transforms/InstCombine/saddo.ll
View File

@ -26,8 +26,7 @@ define i1 @test_constant0(i8 %a) {
define i1 @test_constant1(i8 %a) {
; CHECK-LABEL: @test_constant1(
; CHECK-NEXT: [[RES:%.*]] = tail call { i8, i1 } @llvm.sadd.with.overflow.i8(i8 [[A:%.*]], i8 1)
; CHECK-NEXT: [[OVERFLOW:%.*]] = extractvalue { i8, i1 } [[RES]], 1
; CHECK-NEXT: [[OVERFLOW:%.*]] = icmp eq i8 [[A:%.*]], 127
; CHECK-NEXT: ret i1 [[OVERFLOW]]
;
%res = tail call { i8, i1 } @llvm.sadd.with.overflow.i8(i8 %a, i8 1)
@ -37,8 +36,7 @@ define i1 @test_constant1(i8 %a) {
define i1 @test_constant2(i8 %a) {
; CHECK-LABEL: @test_constant2(
; CHECK-NEXT: [[RES:%.*]] = tail call { i8, i1 } @llvm.sadd.with.overflow.i8(i8 [[A:%.*]], i8 2)
; CHECK-NEXT: [[OVERFLOW:%.*]] = extractvalue { i8, i1 } [[RES]], 1
; CHECK-NEXT: [[OVERFLOW:%.*]] = icmp sgt i8 [[A:%.*]], 125
; CHECK-NEXT: ret i1 [[OVERFLOW]]
;
%res = tail call { i8, i1 } @llvm.sadd.with.overflow.i8(i8 %a, i8 2)
@ -48,8 +46,7 @@ define i1 @test_constant2(i8 %a) {
define i1 @test_constant3(i8 %a) {
; CHECK-LABEL: @test_constant3(
; CHECK-NEXT: [[RES:%.*]] = tail call { i8, i1 } @llvm.sadd.with.overflow.i8(i8 [[A:%.*]], i8 3)
; CHECK-NEXT: [[OVERFLOW:%.*]] = extractvalue { i8, i1 } [[RES]], 1
; CHECK-NEXT: [[OVERFLOW:%.*]] = icmp sgt i8 [[A:%.*]], 124
; CHECK-NEXT: ret i1 [[OVERFLOW]]
;
%res = tail call { i8, i1 } @llvm.sadd.with.overflow.i8(i8 %a, i8 3)
@ -59,8 +56,7 @@ define i1 @test_constant3(i8 %a) {
define i1 @test_constant4(i8 %a) {
; CHECK-LABEL: @test_constant4(
; CHECK-NEXT: [[RES:%.*]] = tail call { i8, i1 } @llvm.sadd.with.overflow.i8(i8 [[A:%.*]], i8 4)
; CHECK-NEXT: [[OVERFLOW:%.*]] = extractvalue { i8, i1 } [[RES]], 1
; CHECK-NEXT: [[OVERFLOW:%.*]] = icmp sgt i8 [[A:%.*]], 123
; CHECK-NEXT: ret i1 [[OVERFLOW]]
;
%res = tail call { i8, i1 } @llvm.sadd.with.overflow.i8(i8 %a, i8 4)
@ -70,8 +66,7 @@ define i1 @test_constant4(i8 %a) {
define i1 @test_constant127(i8 %a) {
; CHECK-LABEL: @test_constant127(
; CHECK-NEXT: [[RES:%.*]] = tail call { i8, i1 } @llvm.sadd.with.overflow.i8(i8 [[A:%.*]], i8 127)
; CHECK-NEXT: [[OVERFLOW:%.*]] = extractvalue { i8, i1 } [[RES]], 1
; CHECK-NEXT: [[OVERFLOW:%.*]] = icmp sgt i8 [[A:%.*]], 0
; CHECK-NEXT: ret i1 [[OVERFLOW]]
;
%res = tail call { i8, i1 } @llvm.sadd.with.overflow.i8(i8 %a, i8 127)
@ -81,8 +76,7 @@ define i1 @test_constant127(i8 %a) {
define i1 @test_constant128(i8 %a) {
; CHECK-LABEL: @test_constant128(
; CHECK-NEXT: [[RES:%.*]] = tail call { i8, i1 } @llvm.sadd.with.overflow.i8(i8 [[A:%.*]], i8 -128)
; CHECK-NEXT: [[OVERFLOW:%.*]] = extractvalue { i8, i1 } [[RES]], 1
; CHECK-NEXT: [[OVERFLOW:%.*]] = icmp slt i8 [[A:%.*]], 0
; CHECK-NEXT: ret i1 [[OVERFLOW]]
;
%res = tail call { i8, i1 } @llvm.sadd.with.overflow.i8(i8 %a, i8 128)
@ -92,8 +86,7 @@ define i1 @test_constant128(i8 %a) {
define i1 @test_constant255(i8 %a) {
; CHECK-LABEL: @test_constant255(
; CHECK-NEXT: [[RES:%.*]] = tail call { i8, i1 } @llvm.sadd.with.overflow.i8(i8 [[A:%.*]], i8 -1)
; CHECK-NEXT: [[OVERFLOW:%.*]] = extractvalue { i8, i1 } [[RES]], 1
; CHECK-NEXT: [[OVERFLOW:%.*]] = icmp eq i8 [[A:%.*]], -128
; CHECK-NEXT: ret i1 [[OVERFLOW]]
;
%res = tail call { i8, i1 } @llvm.sadd.with.overflow.i8(i8 %a, i8 255)

22
test/Transforms/InstCombine/smulo.ll
View File

@ -35,8 +35,8 @@ define i1 @test_constant1(i8 %a) {
define i1 @test_constant2(i8 %a) {
; CHECK-LABEL: @test_constant2(
; CHECK-NEXT: [[RES:%.*]] = tail call { i8, i1 } @llvm.smul.with.overflow.i8(i8 [[A:%.*]], i8 2)
; CHECK-NEXT: [[OVERFLOW:%.*]] = extractvalue { i8, i1 } [[RES]], 1
; CHECK-NEXT: [[TMP1:%.*]] = add i8 [[A:%.*]], 64
; CHECK-NEXT: [[OVERFLOW:%.*]] = icmp slt i8 [[TMP1]], 0
; CHECK-NEXT: ret i1 [[OVERFLOW]]
;
%res = tail call { i8, i1 } @llvm.smul.with.overflow.i8(i8 %a, i8 2)
@ -46,8 +46,8 @@ define i1 @test_constant2(i8 %a) {
define i1 @test_constant3(i8 %a) {
; CHECK-LABEL: @test_constant3(
; CHECK-NEXT: [[RES:%.*]] = tail call { i8, i1 } @llvm.smul.with.overflow.i8(i8 [[A:%.*]], i8 3)
; CHECK-NEXT: [[OVERFLOW:%.*]] = extractvalue { i8, i1 } [[RES]], 1
; CHECK-NEXT: [[TMP1:%.*]] = add i8 [[A:%.*]], 42
; CHECK-NEXT: [[OVERFLOW:%.*]] = icmp ugt i8 [[TMP1]], 84
; CHECK-NEXT: ret i1 [[OVERFLOW]]
;
%res = tail call { i8, i1 } @llvm.smul.with.overflow.i8(i8 %a, i8 3)
@ -57,8 +57,8 @@ define i1 @test_constant3(i8 %a) {
define i1 @test_constant4(i8 %a) {
; CHECK-LABEL: @test_constant4(
; CHECK-NEXT: [[RES:%.*]] = tail call { i8, i1 } @llvm.smul.with.overflow.i8(i8 [[A:%.*]], i8 4)
; CHECK-NEXT: [[OVERFLOW:%.*]] = extractvalue { i8, i1 } [[RES]], 1
; CHECK-NEXT: [[TMP1:%.*]] = add i8 [[A:%.*]], 32
; CHECK-NEXT: [[OVERFLOW:%.*]] = icmp ugt i8 [[TMP1]], 63
; CHECK-NEXT: ret i1 [[OVERFLOW]]
;
%res = tail call { i8, i1 } @llvm.smul.with.overflow.i8(i8 %a, i8 4)
@ -69,8 +69,8 @@ define i1 @test_constant4(i8 %a) {
define i1 @test_constant127(i8 %a) {
; CHECK-LABEL: @test_constant127(
; CHECK-NEXT: [[RES:%.*]] = tail call { i8, i1 } @llvm.smul.with.overflow.i8(i8 [[A:%.*]], i8 127)
; CHECK-NEXT: [[OVERFLOW:%.*]] = extractvalue { i8, i1 } [[RES]], 1
; CHECK-NEXT: [[TMP1:%.*]] = add i8 [[A:%.*]], 1
; CHECK-NEXT: [[OVERFLOW:%.*]] = icmp ugt i8 [[TMP1]], 2
; CHECK-NEXT: ret i1 [[OVERFLOW]]
;
%res = tail call { i8, i1 } @llvm.smul.with.overflow.i8(i8 %a, i8 127)
@ -80,8 +80,7 @@ define i1 @test_constant127(i8 %a) {
define i1 @test_constant128(i8 %a) {
; CHECK-LABEL: @test_constant128(
; CHECK-NEXT: [[RES:%.*]] = tail call { i8, i1 } @llvm.smul.with.overflow.i8(i8 [[A:%.*]], i8 -128)
; CHECK-NEXT: [[OVERFLOW:%.*]] = extractvalue { i8, i1 } [[RES]], 1
; CHECK-NEXT: [[OVERFLOW:%.*]] = icmp ugt i8 [[A:%.*]], 1
; CHECK-NEXT: ret i1 [[OVERFLOW]]
;
%res = tail call { i8, i1 } @llvm.smul.with.overflow.i8(i8 %a, i8 128)
@ -91,8 +90,7 @@ define i1 @test_constant128(i8 %a) {
define i1 @test_constant255(i8 %a) {
; CHECK-LABEL: @test_constant255(
; CHECK-NEXT: [[RES:%.*]] = tail call { i8, i1 } @llvm.smul.with.overflow.i8(i8 [[A:%.*]], i8 -1)
; CHECK-NEXT: [[OVERFLOW:%.*]] = extractvalue { i8, i1 } [[RES]], 1
; CHECK-NEXT: [[OVERFLOW:%.*]] = icmp eq i8 [[A:%.*]], -128
; CHECK-NEXT: ret i1 [[OVERFLOW]]
;
%res = tail call { i8, i1 } @llvm.smul.with.overflow.i8(i8 %a, i8 255)

21
test/Transforms/InstCombine/ssubo.ll
View File

@ -26,8 +26,7 @@ define i1 @test_constant0(i8 %a) {
define i1 @test_constant1(i8 %a) {
; CHECK-LABEL: @test_constant1(
; CHECK-NEXT: [[TMP1:%.*]] = call { i8, i1 } @llvm.sadd.with.overflow.i8(i8 [[A:%.*]], i8 -1)
; CHECK-NEXT: [[OVERFLOW:%.*]] = extractvalue { i8, i1 } [[TMP1]], 1
; CHECK-NEXT: [[OVERFLOW:%.*]] = icmp eq i8 [[A:%.*]], -128
; CHECK-NEXT: ret i1 [[OVERFLOW]]
;
%res = tail call { i8, i1 } @llvm.ssub.with.overflow.i8(i8 %a, i8 1)
@ -37,8 +36,7 @@ define i1 @test_constant1(i8 %a) {
define i1 @test_constant2(i8 %a) {
; CHECK-LABEL: @test_constant2(
; CHECK-NEXT: [[TMP1:%.*]] = call { i8, i1 } @llvm.sadd.with.overflow.i8(i8 [[A:%.*]], i8 -2)
; CHECK-NEXT: [[OVERFLOW:%.*]] = extractvalue { i8, i1 } [[TMP1]], 1
; CHECK-NEXT: [[OVERFLOW:%.*]] = icmp slt i8 [[A:%.*]], -126
; CHECK-NEXT: ret i1 [[OVERFLOW]]
;
%res = tail call { i8, i1 } @llvm.ssub.with.overflow.i8(i8 %a, i8 2)
@ -48,8 +46,7 @@ define i1 @test_constant2(i8 %a) {
define i1 @test_constant3(i8 %a) {
; CHECK-LABEL: @test_constant3(
; CHECK-NEXT: [[TMP1:%.*]] = call { i8, i1 } @llvm.sadd.with.overflow.i8(i8 [[A:%.*]], i8 -3)
; CHECK-NEXT: [[OVERFLOW:%.*]] = extractvalue { i8, i1 } [[TMP1]], 1
; CHECK-NEXT: [[OVERFLOW:%.*]] = icmp slt i8 [[A:%.*]], -125
; CHECK-NEXT: ret i1 [[OVERFLOW]]
;
%res = tail call { i8, i1 } @llvm.ssub.with.overflow.i8(i8 %a, i8 3)
@ -59,8 +56,7 @@ define i1 @test_constant3(i8 %a) {
define i1 @test_constant4(i8 %a) {
; CHECK-LABEL: @test_constant4(
; CHECK-NEXT: [[TMP1:%.*]] = call { i8, i1 } @llvm.sadd.with.overflow.i8(i8 [[A:%.*]], i8 -4)
; CHECK-NEXT: [[OVERFLOW:%.*]] = extractvalue { i8, i1 } [[TMP1]], 1
; CHECK-NEXT: [[OVERFLOW:%.*]] = icmp slt i8 [[A:%.*]], -124
; CHECK-NEXT: ret i1 [[OVERFLOW]]
;
%res = tail call { i8, i1 } @llvm.ssub.with.overflow.i8(i8 %a, i8 4)
@ -71,8 +67,7 @@ define i1 @test_constant4(i8 %a) {
define i1 @test_constant127(i8 %a) {
; CHECK-LABEL: @test_constant127(
; CHECK-NEXT: [[TMP1:%.*]] = call { i8, i1 } @llvm.sadd.with.overflow.i8(i8 [[A:%.*]], i8 -127)
; CHECK-NEXT: [[OVERFLOW:%.*]] = extractvalue { i8, i1 } [[TMP1]], 1
; CHECK-NEXT: [[OVERFLOW:%.*]] = icmp slt i8 [[A:%.*]], -1
; CHECK-NEXT: ret i1 [[OVERFLOW]]
;
%res = tail call { i8, i1 } @llvm.ssub.with.overflow.i8(i8 %a, i8 127)
@ -82,8 +77,7 @@ define i1 @test_constant127(i8 %a) {
define i1 @test_constant128(i8 %a) {
; CHECK-LABEL: @test_constant128(
; CHECK-NEXT: [[RES:%.*]] = tail call { i8, i1 } @llvm.ssub.with.overflow.i8(i8 [[A:%.*]], i8 -128)
; CHECK-NEXT: [[OVERFLOW:%.*]] = extractvalue { i8, i1 } [[RES]], 1
; CHECK-NEXT: [[OVERFLOW:%.*]] = icmp sgt i8 [[A:%.*]], -1
; CHECK-NEXT: ret i1 [[OVERFLOW]]
;
%res = tail call { i8, i1 } @llvm.ssub.with.overflow.i8(i8 %a, i8 128)
@ -93,8 +87,7 @@ define i1 @test_constant128(i8 %a) {
define i1 @test_constant255(i8 %a) {
; CHECK-LABEL: @test_constant255(
; CHECK-NEXT: [[TMP1:%.*]] = call { i8, i1 } @llvm.sadd.with.overflow.i8(i8 [[A:%.*]], i8 1)
; CHECK-NEXT: [[OVERFLOW:%.*]] = extractvalue { i8, i1 } [[TMP1]], 1
; CHECK-NEXT: [[OVERFLOW:%.*]] = icmp eq i8 [[A:%.*]], 127
; CHECK-NEXT: ret i1 [[OVERFLOW]]
;
%res = tail call { i8, i1 } @llvm.ssub.with.overflow.i8(i8 %a, i8 255)

21
test/Transforms/InstCombine/usubo.ll
View File

@ -26,8 +26,7 @@ define i1 @test_constant0(i8 %a) {
define i1 @test_constant1(i8 %a) {
; CHECK-LABEL: @test_constant1(
; CHECK-NEXT: [[RES:%.*]] = tail call { i8, i1 } @llvm.usub.with.overflow.i8(i8 [[A:%.*]], i8 1)
; CHECK-NEXT: [[OVERFLOW:%.*]] = extractvalue { i8, i1 } [[RES]], 1
; CHECK-NEXT: [[OVERFLOW:%.*]] = icmp eq i8 [[A:%.*]], 0
; CHECK-NEXT: ret i1 [[OVERFLOW]]
;
%res = tail call { i8, i1 } @llvm.usub.with.overflow.i8(i8 %a, i8 1)
@ -37,8 +36,7 @@ define i1 @test_constant1(i8 %a) {
define i1 @test_constant2(i8 %a) {
; CHECK-LABEL: @test_constant2(
; CHECK-NEXT: [[RES:%.*]] = tail call { i8, i1 } @llvm.usub.with.overflow.i8(i8 [[A:%.*]], i8 2)
; CHECK-NEXT: [[OVERFLOW:%.*]] = extractvalue { i8, i1 } [[RES]], 1
; CHECK-NEXT: [[OVERFLOW:%.*]] = icmp ult i8 [[A:%.*]], 2
; CHECK-NEXT: ret i1 [[OVERFLOW]]
;
%res = tail call { i8, i1 } @llvm.usub.with.overflow.i8(i8 %a, i8 2)
@ -48,8 +46,7 @@ define i1 @test_constant2(i8 %a) {
define i1 @test_constant3(i8 %a) {
; CHECK-LABEL: @test_constant3(
; CHECK-NEXT: [[RES:%.*]] = tail call { i8, i1 } @llvm.usub.with.overflow.i8(i8 [[A:%.*]], i8 3)
; CHECK-NEXT: [[OVERFLOW:%.*]] = extractvalue { i8, i1 } [[RES]], 1
; CHECK-NEXT: [[OVERFLOW:%.*]] = icmp ult i8 [[A:%.*]], 3
; CHECK-NEXT: ret i1 [[OVERFLOW]]
;
%res = tail call { i8, i1 } @llvm.usub.with.overflow.i8(i8 %a, i8 3)
@ -59,8 +56,7 @@ define i1 @test_constant3(i8 %a) {
define i1 @test_constant4(i8 %a) {
; CHECK-LABEL: @test_constant4(
; CHECK-NEXT: [[RES:%.*]] = tail call { i8, i1 } @llvm.usub.with.overflow.i8(i8 [[A:%.*]], i8 4)
; CHECK-NEXT: [[OVERFLOW:%.*]] = extractvalue { i8, i1 } [[RES]], 1
; CHECK-NEXT: [[OVERFLOW:%.*]] = icmp ult i8 [[A:%.*]], 4
; CHECK-NEXT: ret i1 [[OVERFLOW]]
;
%res = tail call { i8, i1 } @llvm.usub.with.overflow.i8(i8 %a, i8 4)
@ -71,8 +67,7 @@ define i1 @test_constant4(i8 %a) {
define i1 @test_constant127(i8 %a) {
; CHECK-LABEL: @test_constant127(
; CHECK-NEXT: [[RES:%.*]] = tail call { i8, i1 } @llvm.usub.with.overflow.i8(i8 [[A:%.*]], i8 127)
; CHECK-NEXT: [[OVERFLOW:%.*]] = extractvalue { i8, i1 } [[RES]], 1
; CHECK-NEXT: [[OVERFLOW:%.*]] = icmp ult i8 [[A:%.*]], 127
; CHECK-NEXT: ret i1 [[OVERFLOW]]
;
%res = tail call { i8, i1 } @llvm.usub.with.overflow.i8(i8 %a, i8 127)
@ -82,8 +77,7 @@ define i1 @test_constant127(i8 %a) {
define i1 @test_constant128(i8 %a) {
; CHECK-LABEL: @test_constant128(
; CHECK-NEXT: [[RES:%.*]] = tail call { i8, i1 } @llvm.usub.with.overflow.i8(i8 [[A:%.*]], i8 -128)
; CHECK-NEXT: [[OVERFLOW:%.*]] = extractvalue { i8, i1 } [[RES]], 1
; CHECK-NEXT: [[OVERFLOW:%.*]] = icmp sgt i8 [[A:%.*]], -1
; CHECK-NEXT: ret i1 [[OVERFLOW]]
;
%res = tail call { i8, i1 } @llvm.usub.with.overflow.i8(i8 %a, i8 128)
@ -93,8 +87,7 @@ define i1 @test_constant128(i8 %a) {
define i1 @test_constant255(i8 %a) {
; CHECK-LABEL: @test_constant255(
; CHECK-NEXT: [[RES:%.*]] = tail call { i8, i1 } @llvm.usub.with.overflow.i8(i8 [[A:%.*]], i8 -1)
; CHECK-NEXT: [[OVERFLOW:%.*]] = extractvalue { i8, i1 } [[RES]], 1
; CHECK-NEXT: [[OVERFLOW:%.*]] = icmp ne i8 [[A:%.*]], -1
; CHECK-NEXT: ret i1 [[OVERFLOW]]
;
%res = tail call { i8, i1 } @llvm.usub.with.overflow.i8(i8 %a, i8 255)