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[InstSimplify] Fix addo/subo with undef (PR43188) 

We can't fold the first result to undef, because not all values
may be reachable under the constraint that no overflow occurred.
Use the same folds we do for saturated math instead.

Proofs:
uaddo: https://alive2.llvm.org/ce/z/zf55N_
saddo: https://alive2.llvm.org/ce/z/a_xPgS
usubo: https://alive2.llvm.org/ce/z/DmRqwt
ssubo: https://alive2.llvm.org/ce/z/8ag7U-
This commit is contained in:
Nikita Popov 2021-01-03 18:51:49 +01:00
parent c6ad00d709
commit f094d65bea
3 changed files with 24 additions and 24 deletions
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14
llvm/lib/Analysis/InstructionSimplify.cpp
View File

@ -5444,19 +5444,19 @@ static Value *simplifyBinaryIntrinsic(Function *F, Value *Op0, Value *Op1,
case Intrinsic::usub_with_overflow:
case Intrinsic::ssub_with_overflow:
// X - X -> { 0, false }
if (Op0 == Op1)
// X - undef -> { 0, false }
// undef - X -> { 0, false }
if (Op0 == Op1 || Q.isUndefValue(Op0) || Q.isUndefValue(Op1))
return Constant::getNullValue(ReturnType);
LLVM_FALLTHROUGH;
break;
case Intrinsic::uadd_with_overflow:
case Intrinsic::sadd_with_overflow:
// X - undef -> { undef, false }
// undef - X -> { undef, false }
// X + undef -> { undef, false }
// undef + x -> { undef, false }
// X + undef -> { -1, false }
// undef + x -> { -1, false }
if (Q.isUndefValue(Op0) || Q.isUndefValue(Op1)) {
return ConstantStruct::get(
cast<StructType>(ReturnType),
{UndefValue::get(ReturnType->getStructElementType(0)),
{Constant::getAllOnesValue(ReturnType->getStructElementType(0)),
Constant::getNullValue(ReturnType->getStructElementType(1))});
}
break;

2
llvm/test/Transforms/InstCombine/with_overflow.ll
View File

@ -61,7 +61,7 @@ define i8 @uaddtest3(i8 %A, i8 %B, i1* %overflowPtr) {
define i8 @uaddtest4(i8 %A, i1* %overflowPtr) {
; CHECK-LABEL: @uaddtest4(
; CHECK-NEXT: store i1 false, i1* [[OVERFLOWPTR:%.*]], align 1
; CHECK-NEXT: ret i8 undef
; CHECK-NEXT: ret i8 -1
;
%x = call { i8, i1 } @llvm.uadd.with.overflow.i8(i8 undef, i8 %A)
%y = extractvalue { i8, i1 } %x, 0

32
llvm/test/Transforms/InstSimplify/call.ll
View File

@ -29,7 +29,7 @@ define i8 @test_uadd2() {
define {i8, i1} @test_uadd3(i8 %v) {
; CHECK-LABEL: @test_uadd3(
; CHECK-NEXT: ret { i8, i1 } { i8 undef, i1 false }
; CHECK-NEXT: ret { i8, i1 } { i8 -1, i1 false }
;
%result = call {i8, i1} @llvm.uadd.with.overflow.i8(i8 %v, i8 undef)
ret {i8, i1} %result
@ -37,7 +37,7 @@ define {i8, i1} @test_uadd3(i8 %v) {
define {i8, i1} @test_uadd3_poison(i8 %v) {
; CHECK-LABEL: @test_uadd3_poison(
; CHECK-NEXT: ret { i8, i1 } { i8 undef, i1 false }
; CHECK-NEXT: ret { i8, i1 } { i8 -1, i1 false }
;
%result = call {i8, i1} @llvm.uadd.with.overflow.i8(i8 %v, i8 poison)
ret {i8, i1} %result
@ -45,7 +45,7 @@ define {i8, i1} @test_uadd3_poison(i8 %v) {
define {i8, i1} @test_uadd4(i8 %v) {
; CHECK-LABEL: @test_uadd4(
; CHECK-NEXT: ret { i8, i1 } { i8 undef, i1 false }
; CHECK-NEXT: ret { i8, i1 } { i8 -1, i1 false }
;
%result = call {i8, i1} @llvm.uadd.with.overflow.i8(i8 undef, i8 %v)
ret {i8, i1} %result
@ -53,7 +53,7 @@ define {i8, i1} @test_uadd4(i8 %v) {
define {i8, i1} @test_uadd4_poison(i8 %v) {
; CHECK-LABEL: @test_uadd4_poison(
; CHECK-NEXT: ret { i8, i1 } { i8 undef, i1 false }
; CHECK-NEXT: ret { i8, i1 } { i8 -1, i1 false }
;
%result = call {i8, i1} @llvm.uadd.with.overflow.i8(i8 poison, i8 %v)
ret {i8, i1} %result
@ -79,7 +79,7 @@ define i8 @test_sadd2() {
define {i8, i1} @test_sadd3(i8 %v) {
; CHECK-LABEL: @test_sadd3(
; CHECK-NEXT: ret { i8, i1 } { i8 undef, i1 false }
; CHECK-NEXT: ret { i8, i1 } { i8 -1, i1 false }
;
%result = call {i8, i1} @llvm.sadd.with.overflow.i8(i8 %v, i8 undef)
ret {i8, i1} %result
@ -87,7 +87,7 @@ define {i8, i1} @test_sadd3(i8 %v) {
define {i8, i1} @test_sadd3_poison(i8 %v) {
; CHECK-LABEL: @test_sadd3_poison(
; CHECK-NEXT: ret { i8, i1 } { i8 undef, i1 false }
; CHECK-NEXT: ret { i8, i1 } { i8 -1, i1 false }
;
%result = call {i8, i1} @llvm.sadd.with.overflow.i8(i8 %v, i8 poison)
ret {i8, i1} %result
@ -95,7 +95,7 @@ define {i8, i1} @test_sadd3_poison(i8 %v) {
define {i8, i1} @test_sadd4(i8 %v) {
; CHECK-LABEL: @test_sadd4(
; CHECK-NEXT: ret { i8, i1 } { i8 undef, i1 false }
; CHECK-NEXT: ret { i8, i1 } { i8 -1, i1 false }
;
%result = call {i8, i1} @llvm.sadd.with.overflow.i8(i8 undef, i8 %v)
ret {i8, i1} %result
@ -103,7 +103,7 @@ define {i8, i1} @test_sadd4(i8 %v) {
define {i8, i1} @test_sadd4_poison(i8 %v) {
; CHECK-LABEL: @test_sadd4_poison(
; CHECK-NEXT: ret { i8, i1 } { i8 undef, i1 false }
; CHECK-NEXT: ret { i8, i1 } { i8 -1, i1 false }
;
%result = call {i8, i1} @llvm.sadd.with.overflow.i8(i8 poison, i8 %v)
ret {i8, i1} %result
@ -119,7 +119,7 @@ define {i8, i1} @test_usub1(i8 %V) {
define {i8, i1} @test_usub2(i8 %V) {
; CHECK-LABEL: @test_usub2(
; CHECK-NEXT: ret { i8, i1 } { i8 undef, i1 false }
; CHECK-NEXT: ret { i8, i1 } zeroinitializer
;
%x = call {i8, i1} @llvm.usub.with.overflow.i8(i8 %V, i8 undef)
ret {i8, i1} %x
@ -127,7 +127,7 @@ define {i8, i1} @test_usub2(i8 %V) {
define {i8, i1} @test_usub2_poison(i8 %V) {
; CHECK-LABEL: @test_usub2_poison(
; CHECK-NEXT: ret { i8, i1 } { i8 undef, i1 false }
; CHECK-NEXT: ret { i8, i1 } zeroinitializer
;
%x = call {i8, i1} @llvm.usub.with.overflow.i8(i8 %V, i8 poison)
ret {i8, i1} %x
@ -135,7 +135,7 @@ define {i8, i1} @test_usub2_poison(i8 %V) {
define {i8, i1} @test_usub3(i8 %V) {
; CHECK-LABEL: @test_usub3(
; CHECK-NEXT: ret { i8, i1 } { i8 undef, i1 false }
; CHECK-NEXT: ret { i8, i1 } zeroinitializer
;
%x = call {i8, i1} @llvm.usub.with.overflow.i8(i8 undef, i8 %V)
ret {i8, i1} %x
@ -143,7 +143,7 @@ define {i8, i1} @test_usub3(i8 %V) {
define {i8, i1} @test_usub3_poison(i8 %V) {
; CHECK-LABEL: @test_usub3_poison(
; CHECK-NEXT: ret { i8, i1 } { i8 undef, i1 false }
; CHECK-NEXT: ret { i8, i1 } zeroinitializer
;
%x = call {i8, i1} @llvm.usub.with.overflow.i8(i8 poison, i8 %V)
ret {i8, i1} %x
@ -159,7 +159,7 @@ define {i8, i1} @test_ssub1(i8 %V) {
define {i8, i1} @test_ssub2(i8 %V) {
; CHECK-LABEL: @test_ssub2(
; CHECK-NEXT: ret { i8, i1 } { i8 undef, i1 false }
; CHECK-NEXT: ret { i8, i1 } zeroinitializer
;
%x = call {i8, i1} @llvm.ssub.with.overflow.i8(i8 %V, i8 undef)
ret {i8, i1} %x
@ -167,7 +167,7 @@ define {i8, i1} @test_ssub2(i8 %V) {
define {i8, i1} @test_ssub2_poison(i8 %V) {
; CHECK-LABEL: @test_ssub2_poison(
; CHECK-NEXT: ret { i8, i1 } { i8 undef, i1 false }
; CHECK-NEXT: ret { i8, i1 } zeroinitializer
;
%x = call {i8, i1} @llvm.ssub.with.overflow.i8(i8 %V, i8 poison)
ret {i8, i1} %x
@ -175,7 +175,7 @@ define {i8, i1} @test_ssub2_poison(i8 %V) {
define {i8, i1} @test_ssub3(i8 %V) {
; CHECK-LABEL: @test_ssub3(
; CHECK-NEXT: ret { i8, i1 } { i8 undef, i1 false }
; CHECK-NEXT: ret { i8, i1 } zeroinitializer
;
%x = call {i8, i1} @llvm.ssub.with.overflow.i8(i8 undef, i8 %V)
ret {i8, i1} %x
@ -183,7 +183,7 @@ define {i8, i1} @test_ssub3(i8 %V) {
define {i8, i1} @test_ssub3_poison(i8 %V) {
; CHECK-LABEL: @test_ssub3_poison(
; CHECK-NEXT: ret { i8, i1 } { i8 undef, i1 false }
; CHECK-NEXT: ret { i8, i1 } zeroinitializer
;
%x = call {i8, i1} @llvm.ssub.with.overflow.i8(i8 poison, i8 %V)
ret {i8, i1} %x