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[CVP] Try to fold sdiv to constant

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If we know that the sdiv result is a single constant, directly
use that instead of performing narrowing.

Fixes https://github.com/llvm/llvm-project/issues/71659.
This commit is contained in:
Nikita Popov
2023-11-08 14:10:39 +01:00
parent dc2cfd0407
commit d687057de8
2 changed files with 10 additions and 14 deletions
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7
llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
View File

@@ -910,6 +910,13 @@ static bool processSDiv(BinaryOperator *SDI, const ConstantRange &LCR,
assert(SDI->getOpcode() == Instruction::SDiv);
assert(!SDI->getType()->isVectorTy());
// Check whether the division folds to a constant.
if (const APInt *Elem = LCR.sdiv(RCR).getSingleElement()) {
SDI->replaceAllUsesWith(ConstantInt::get(SDI->getType(), *Elem));
SDI->eraseFromParent();
return true;
}
struct Operand {
Value *V;
Domain D;

17
llvm/test/Transforms/CorrelatedValuePropagation/sdiv.ll
View File

@@ -638,10 +638,7 @@ define void @sdiv_zero(ptr %p, i32 %arg) {
; CHECK-NEXT: [[ADD:%.*]] = add i32 [[ARG:%.*]], 5
; CHECK-NEXT: [[CMP:%.*]] = icmp ult i32 [[ADD]], 11
; CHECK-NEXT: call void @llvm.assume(i1 [[CMP]])
; CHECK-NEXT: [[DIV_LHS_TRUNC:%.*]] = trunc i32 [[ARG]] to i8
; CHECK-NEXT: [[DIV1:%.*]] = sdiv i8 [[DIV_LHS_TRUNC]], 6
; CHECK-NEXT: [[DIV_SEXT:%.*]] = sext i8 [[DIV1]] to i32
; CHECK-NEXT: store i32 [[DIV_SEXT]], ptr [[P:%.*]], align 4
; CHECK-NEXT: store i32 0, ptr [[P:%.*]], align 4
; CHECK-NEXT: ret void
;
%add = add i32 %arg, 5
@@ -676,10 +673,7 @@ define void @sdiv_pos(ptr %p, i32 %arg) {
; CHECK-NEXT: [[ADD:%.*]] = add i32 [[ARG:%.*]], -12
; CHECK-NEXT: [[CMP:%.*]] = icmp ult i32 [[ADD]], 6
; CHECK-NEXT: call void @llvm.assume(i1 [[CMP]])
; CHECK-NEXT: [[DIV1_LHS_TRUNC:%.*]] = trunc i32 [[ARG]] to i8
; CHECK-NEXT: [[DIV12:%.*]] = udiv i8 [[DIV1_LHS_TRUNC]], 6
; CHECK-NEXT: [[DIV1_ZEXT:%.*]] = zext i8 [[DIV12]] to i32
; CHECK-NEXT: store i32 [[DIV1_ZEXT]], ptr [[P:%.*]], align 4
; CHECK-NEXT: store i32 2, ptr [[P:%.*]], align 4
; CHECK-NEXT: ret void
;
%add = add i32 %arg, -12
@@ -695,12 +689,7 @@ define void @sdiv_neg(ptr %p, i32 %arg) {
; CHECK-NEXT: [[ADD:%.*]] = add i32 [[ARG:%.*]], 17
; CHECK-NEXT: [[CMP:%.*]] = icmp ult i32 [[ADD]], 6
; CHECK-NEXT: call void @llvm.assume(i1 [[CMP]])
; CHECK-NEXT: [[ARG_NONNEG:%.*]] = sub i32 0, [[ARG]]
; CHECK-NEXT: [[DIV1_LHS_TRUNC:%.*]] = trunc i32 [[ARG_NONNEG]] to i8
; CHECK-NEXT: [[DIV12:%.*]] = udiv i8 [[DIV1_LHS_TRUNC]], 6
; CHECK-NEXT: [[DIV1_ZEXT:%.*]] = zext i8 [[DIV12]] to i32
; CHECK-NEXT: [[DIV1_NEG:%.*]] = sub i32 0, [[DIV1_ZEXT]]
; CHECK-NEXT: store i32 [[DIV1_NEG]], ptr [[P:%.*]], align 4
; CHECK-NEXT: store i32 -2, ptr [[P:%.*]], align 4
; CHECK-NEXT: ret void
;
%add = add i32 %arg, 17