[llvm] [InstCombine] Add missing patterns for scmp and ucmp (PR #149225)
via llvm-commits
llvm-commits at lists.llvm.org
Wed Jul 16 19:01:55 PDT 2025
https://github.com/AZero13 updated https://github.com/llvm/llvm-project/pull/149225
>From b72397b792ba01f19f4edba4bfb7770c7fef0176 Mon Sep 17 00:00:00 2001
From: Rose <gfunni234 at gmail.com>
Date: Wed, 16 Jul 2025 16:38:24 -0400
Subject: [PATCH 1/2] Pre-commit test (NFC)
---
llvm/test/Transforms/InstCombine/scmp.ll | 101 +++++++++++++++++++++++
1 file changed, 101 insertions(+)
diff --git a/llvm/test/Transforms/InstCombine/scmp.ll b/llvm/test/Transforms/InstCombine/scmp.ll
index 2bf22aeb7a6e9..323ef9e9d53e9 100644
--- a/llvm/test/Transforms/InstCombine/scmp.ll
+++ b/llvm/test/Transforms/InstCombine/scmp.ll
@@ -436,6 +436,107 @@ define <3 x i2> @scmp_unary_shuffle_ops(<3 x i8> %x, <3 x i8> %y) {
ret <3 x i2> %r
}
+define i32 @scmp_ashr(i32 %a) {
+; CHECK-LABEL: define i32 @scmp_ashr(
+; CHECK-SAME: i32 [[A:%.*]]) {
+; CHECK-NEXT: [[A_LOBIT:%.*]] = ashr i32 [[A]], 31
+; CHECK-NEXT: [[CMP_INV:%.*]] = icmp slt i32 [[A]], 1
+; CHECK-NEXT: [[RETVAL_0:%.*]] = select i1 [[CMP_INV]], i32 [[A_LOBIT]], i32 1
+; CHECK-NEXT: ret i32 [[RETVAL_0]]
+;
+ %a.lobit = ashr i32 %a, 31
+ %cmp.inv = icmp slt i32 %a, 1
+ %retval.0 = select i1 %cmp.inv, i32 %a.lobit, i32 1
+ ret i32 %retval.0
+}
+
+define i32 @scmp_sgt_slt(i32 %a) {
+; CHECK-LABEL: define i32 @scmp_sgt_slt(
+; CHECK-SAME: i32 [[A:%.*]]) {
+; CHECK-NEXT: [[A_LOBIT:%.*]] = ashr i32 [[A]], 31
+; CHECK-NEXT: [[CMP_INV:%.*]] = icmp slt i32 [[A]], 1
+; CHECK-NEXT: [[RETVAL_0:%.*]] = select i1 [[CMP_INV]], i32 [[A_LOBIT]], i32 1
+; CHECK-NEXT: ret i32 [[RETVAL_0]]
+;
+ %cmp = icmp sgt i32 %a, 0
+ %cmp1 = icmp slt i32 %a, 0
+ %. = select i1 %cmp1, i32 -1, i32 0
+ %retval.0 = select i1 %cmp, i32 1, i32 %.
+ ret i32 %retval.0
+}
+
+define i32 @scmp_zero_slt(i32 %a) {
+; CHECK-LABEL: define i32 @scmp_zero_slt(
+; CHECK-SAME: i32 [[A:%.*]]) {
+; CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[A]], 0
+; CHECK-NEXT: [[CMP1_INV:%.*]] = icmp slt i32 [[A]], 1
+; CHECK-NEXT: [[DOT:%.*]] = select i1 [[CMP1_INV]], i32 -1, i32 1
+; CHECK-NEXT: [[RETVAL_0:%.*]] = select i1 [[CMP]], i32 0, i32 [[DOT]]
+; CHECK-NEXT: ret i32 [[RETVAL_0]]
+;
+ %cmp = icmp eq i32 %a, 0
+ %cmp1.inv = icmp slt i32 %a, 1
+ %. = select i1 %cmp1.inv, i32 -1, i32 1
+ %retval.0 = select i1 %cmp, i32 0, i32 %.
+ ret i32 %retval.0
+}
+
+define i32 @scmp_zero_sgt(i32 %a) {
+; CHECK-LABEL: define i32 @scmp_zero_sgt(
+; CHECK-SAME: i32 [[A:%.*]]) {
+; CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[A]], 0
+; CHECK-NEXT: [[CMP1_INV:%.*]] = icmp sgt i32 [[A]], -1
+; CHECK-NEXT: [[DOT:%.*]] = select i1 [[CMP1_INV]], i32 1, i32 -1
+; CHECK-NEXT: [[RETVAL_0:%.*]] = select i1 [[CMP]], i32 0, i32 [[DOT]]
+; CHECK-NEXT: ret i32 [[RETVAL_0]]
+;
+ %cmp = icmp eq i32 %a, 0
+ %cmp1.inv = icmp sgt i32 %a, -1
+ %. = select i1 %cmp1.inv, i32 1, i32 -1
+ %retval.0 = select i1 %cmp, i32 0, i32 %.
+ ret i32 %retval.0
+}
+
+
+define i32 @scmp_sgt_slt_ab(i32 %a, i32 %b) {
+; CHECK-LABEL: define i32 @scmp_sgt_slt_ab(
+; CHECK-SAME: i32 [[A:%.*]], i32 [[B:%.*]]) {
+; CHECK-NEXT: [[RETVAL_0:%.*]] = call i32 @llvm.scmp.i32.i32(i32 [[A]], i32 [[B]])
+; CHECK-NEXT: ret i32 [[RETVAL_0]]
+;
+ %cmp = icmp sgt i32 %a, %b
+ %cmp1 = icmp slt i32 %a, %b
+ %. = select i1 %cmp1, i32 -1, i32 0
+ %retval.0 = select i1 %cmp, i32 1, i32 %.
+ ret i32 %retval.0
+}
+
+define i32 @scmp_zero_slt_ab(i32 %a, i32 %b) {
+; CHECK-LABEL: define i32 @scmp_zero_slt_ab(
+; CHECK-SAME: i32 [[A:%.*]], i32 [[B:%.*]]) {
+; CHECK-NEXT: [[RETVAL_0:%.*]] = call i32 @llvm.scmp.i32.i32(i32 [[A]], i32 [[B]])
+; CHECK-NEXT: ret i32 [[RETVAL_0]]
+;
+ %cmp = icmp eq i32 %a, %b
+ %cmp1.inv = icmp slt i32 %a, %b
+ %. = select i1 %cmp1.inv, i32 -1, i32 1
+ %retval.0 = select i1 %cmp, i32 0, i32 %.
+ ret i32 %retval.0
+}
+
+define i32 @scmp_zero_sgt_ab(i32 %a, i32 %b) {
+; CHECK-LABEL: define i32 @scmp_zero_sgt_ab(
+; CHECK-SAME: i32 [[A:%.*]], i32 [[B:%.*]]) {
+; CHECK-NEXT: [[RETVAL_0:%.*]] = call i32 @llvm.scmp.i32.i32(i32 [[A]], i32 [[B]])
+; CHECK-NEXT: ret i32 [[RETVAL_0]]
+;
+ %cmp = icmp eq i32 %a, %b
+ %cmp1.inv = icmp sgt i32 %a, %b
+ %. = select i1 %cmp1.inv, i32 1, i32 -1
+ %retval.0 = select i1 %cmp, i32 0, i32 %.
+ ret i32 %retval.0
+}
+
; Negative test: true value of outer select is not zero
define i8 @scmp_from_select_eq_and_gt_neg1(i32 %x, i32 %y) {
; CHECK-LABEL: define i8 @scmp_from_select_eq_and_gt_neg1(
>From d4a2a2b565df83d157493950b4ca7dea09e7c87f Mon Sep 17 00:00:00 2001
From: Rose <gfunni234 at gmail.com>
Date: Wed, 16 Jul 2025 16:55:20 -0400
Subject: [PATCH 2/2] [InstCombine] Add missing patterns for scmp and ucmp
Fixes: https://github.com/llvm/llvm-project/issues/146178
---
.../InstCombine/InstCombineSelect.cpp | 58 +++++++++
llvm/test/Transforms/InstCombine/scmp.ll | 118 +++++++++++++++---
2 files changed, 162 insertions(+), 14 deletions(-)
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
index 73ba0f78e8053..a615505fd4f73 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
@@ -3635,6 +3635,10 @@ static Instruction *foldBitCeil(SelectInst &SI, IRBuilderBase &Builder,
// (x < y) ? -1 : zext(x > y)
// (x > y) ? 1 : sext(x != y)
// (x > y) ? 1 : sext(x < y)
+// (x == y) ? 0 : (x > y ? 1 : -1)
+// (x == y) ? 0 : (x < y ? -1 : 1)
+// Special case: x == C ? 0 : (x > C - 1 ? 1 : -1)
+// Special case: x == C ? 0 : (x < C + 1 ? -1 : 1)
// Into ucmp/scmp(x, y), where signedness is determined by the signedness
// of the comparison in the original sequence.
Instruction *InstCombinerImpl::foldSelectToCmp(SelectInst &SI) {
@@ -3727,6 +3731,45 @@ Instruction *InstCombinerImpl::foldSelectToCmp(SelectInst &SI) {
}
}
+ // Special cases with constants: x == C ? 0 : (x > C-1 ? 1 : -1)
+ if (Pred == ICmpInst::ICMP_EQ && match(TV, m_Zero())) {
+ Value *X;
+ const APInt *C;
+ if (match(LHS, m_Value(X)) && match(RHS, m_APInt(C))) {
+ CmpPredicate InnerPred;
+ Value *InnerLHS, *InnerRHS;
+ const APInt *InnerTV, *InnerFV;
+ if (match(FV, m_Select(
+ m_ICmp(InnerPred, m_Value(InnerLHS), m_Value(InnerRHS)),
+ m_APInt(InnerTV), m_APInt(InnerFV)))) {
+
+ // x == C ? 0 : (x > C-1 ? 1 : -1)
+ if (ICmpInst::isGT(InnerPred) && InnerTV->isOne() &&
+ InnerFV->isAllOnes()) {
+ IsSigned = ICmpInst::isSigned(InnerPred);
+ bool CanSubOne = IsSigned ? !C->isMinSignedValue() : !C->isMinValue();
+ if (CanSubOne) {
+ APInt Cminus1 = *C - 1;
+ if (InnerLHS == X && match(InnerRHS, m_SpecificInt(Cminus1)))
+ Replace = true;
+ }
+ }
+
+ // x == C ? 0 : (x < C+1 ? -1 : 1)
+ if (ICmpInst::isLT(InnerPred) && InnerTV->isAllOnes() &&
+ InnerFV->isOne()) {
+ IsSigned = ICmpInst::isSigned(InnerPred);
+ bool CanAddOne = IsSigned ? !C->isMaxSignedValue() : !C->isMaxValue();
+ if (CanAddOne) {
+ APInt Cplus1 = *C + 1;
+ if (InnerLHS == X && match(InnerRHS, m_SpecificInt(Cplus1)))
+ Replace = true;
+ }
+ }
+ }
+ }
+ }
+
Intrinsic::ID IID = IsSigned ? Intrinsic::scmp : Intrinsic::ucmp;
if (Replace)
return replaceInstUsesWith(
@@ -4496,5 +4539,20 @@ Instruction *InstCombinerImpl::visitSelectInst(SelectInst &SI) {
return replaceOperand(SI, 2, ConstantInt::get(FalseVal->getType(), 0));
}
+ // Canonicalize sign function ashr pattern: select (icmp slt X, 1), ashr X,
+ // bitwidth-1, 1 -> scmp(X, 0)
+ Value *X;
+ unsigned BitWidth = SI.getType()->getScalarSizeInBits();
+ CmpPredicate Pred;
+ if (match(&SI, m_Select(m_ICmp(Pred, m_Value(X), m_One()),
+ m_AShr(m_Deferred(X), m_SpecificInt(BitWidth - 1)),
+ m_One())) &&
+ Pred == ICmpInst::ICMP_SLT) {
+
+ Function *Scmp = Intrinsic::getOrInsertDeclaration(
+ SI.getModule(), Intrinsic::scmp, {SI.getType(), SI.getType()});
+ return CallInst::Create(Scmp, {X, ConstantInt::get(SI.getType(), 0)});
+ }
+
return nullptr;
}
diff --git a/llvm/test/Transforms/InstCombine/scmp.ll b/llvm/test/Transforms/InstCombine/scmp.ll
index 323ef9e9d53e9..972965eaa6fc2 100644
--- a/llvm/test/Transforms/InstCombine/scmp.ll
+++ b/llvm/test/Transforms/InstCombine/scmp.ll
@@ -439,9 +439,7 @@ define <3 x i2> @scmp_unary_shuffle_ops(<3 x i8> %x, <3 x i8> %y) {
define i32 @scmp_ashr(i32 %a) {
; CHECK-LABEL: define i32 @scmp_ashr(
; CHECK-SAME: i32 [[A:%.*]]) {
-; CHECK-NEXT: [[A_LOBIT:%.*]] = ashr i32 [[A]], 31
-; CHECK-NEXT: [[CMP_INV:%.*]] = icmp slt i32 [[A]], 1
-; CHECK-NEXT: [[RETVAL_0:%.*]] = select i1 [[CMP_INV]], i32 [[A_LOBIT]], i32 1
+; CHECK-NEXT: [[RETVAL_0:%.*]] = call i32 @llvm.scmp.i32.i32(i32 [[A]], i32 0)
; CHECK-NEXT: ret i32 [[RETVAL_0]]
;
%a.lobit = ashr i32 %a, 31
@@ -453,9 +451,7 @@ define i32 @scmp_ashr(i32 %a) {
define i32 @scmp_sgt_slt(i32 %a) {
; CHECK-LABEL: define i32 @scmp_sgt_slt(
; CHECK-SAME: i32 [[A:%.*]]) {
-; CHECK-NEXT: [[A_LOBIT:%.*]] = ashr i32 [[A]], 31
-; CHECK-NEXT: [[CMP_INV:%.*]] = icmp slt i32 [[A]], 1
-; CHECK-NEXT: [[RETVAL_0:%.*]] = select i1 [[CMP_INV]], i32 [[A_LOBIT]], i32 1
+; CHECK-NEXT: [[RETVAL_0:%.*]] = call i32 @llvm.scmp.i32.i32(i32 [[A]], i32 0)
; CHECK-NEXT: ret i32 [[RETVAL_0]]
;
%cmp = icmp sgt i32 %a, 0
@@ -468,10 +464,7 @@ define i32 @scmp_sgt_slt(i32 %a) {
define i32 @scmp_zero_slt(i32 %a) {
; CHECK-LABEL: define i32 @scmp_zero_slt(
; CHECK-SAME: i32 [[A:%.*]]) {
-; CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[A]], 0
-; CHECK-NEXT: [[CMP1_INV:%.*]] = icmp slt i32 [[A]], 1
-; CHECK-NEXT: [[DOT:%.*]] = select i1 [[CMP1_INV]], i32 -1, i32 1
-; CHECK-NEXT: [[RETVAL_0:%.*]] = select i1 [[CMP]], i32 0, i32 [[DOT]]
+; CHECK-NEXT: [[RETVAL_0:%.*]] = call i32 @llvm.scmp.i32.i32(i32 [[A]], i32 0)
; CHECK-NEXT: ret i32 [[RETVAL_0]]
;
%cmp = icmp eq i32 %a, 0
@@ -484,10 +477,7 @@ define i32 @scmp_zero_slt(i32 %a) {
define i32 @scmp_zero_sgt(i32 %a) {
; CHECK-LABEL: define i32 @scmp_zero_sgt(
; CHECK-SAME: i32 [[A:%.*]]) {
-; CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[A]], 0
-; CHECK-NEXT: [[CMP1_INV:%.*]] = icmp sgt i32 [[A]], -1
-; CHECK-NEXT: [[DOT:%.*]] = select i1 [[CMP1_INV]], i32 1, i32 -1
-; CHECK-NEXT: [[RETVAL_0:%.*]] = select i1 [[CMP]], i32 0, i32 [[DOT]]
+; CHECK-NEXT: [[RETVAL_0:%.*]] = call i32 @llvm.scmp.i32.i32(i32 [[A]], i32 0)
; CHECK-NEXT: ret i32 [[RETVAL_0]]
;
%cmp = icmp eq i32 %a, 0
@@ -498,6 +488,106 @@ define i32 @scmp_zero_sgt(i32 %a) {
}
+define i32 @scmp_zero_sgt_1(i32 %a) {
+; CHECK-LABEL: define i32 @scmp_zero_sgt_1(
+; CHECK-SAME: i32 [[A:%.*]]) {
+; CHECK-NEXT: [[COND2:%.*]] = call i32 @llvm.scmp.i32.i32(i32 [[A]], i32 0)
+; CHECK-NEXT: ret i32 [[COND2]]
+;
+ %cmp = icmp eq i32 %a, 0
+ %cmp1 = icmp sgt i32 %a, -1
+ %cond = select i1 %cmp1, i32 1, i32 -1
+ %cond2 = select i1 %cmp, i32 0, i32 %cond
+ ret i32 %cond2
+}
+
+define i32 @scmp_zero_slt_1(i32 %a) {
+; CHECK-LABEL: define i32 @scmp_zero_slt_1(
+; CHECK-SAME: i32 [[A:%.*]]) {
+; CHECK-NEXT: [[COND2:%.*]] = call i32 @llvm.scmp.i32.i32(i32 [[A]], i32 0)
+; CHECK-NEXT: ret i32 [[COND2]]
+;
+ %cmp = icmp eq i32 %a, 0
+ %cmp1 = icmp slt i32 %a, 1
+ %cond = select i1 %cmp1, i32 -1, i32 1
+ %cond2 = select i1 %cmp, i32 0, i32 %cond
+ ret i32 %cond2
+}
+
+define i32 @scmp_zero_slt_neg(i32 %a) {
+; CHECK-LABEL: define i32 @scmp_zero_slt_neg(
+; CHECK-SAME: i32 [[A:%.*]]) {
+; CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[A]], 0
+; CHECK-NEXT: [[CMP1:%.*]] = icmp slt i32 [[A]], -1
+; CHECK-NEXT: [[COND:%.*]] = select i1 [[CMP1]], i32 -1, i32 1
+; CHECK-NEXT: [[COND2:%.*]] = select i1 [[CMP]], i32 0, i32 [[COND]]
+; CHECK-NEXT: ret i32 [[COND2]]
+;
+ %cmp = icmp eq i32 %a, 0
+ %cmp1 = icmp slt i32 %a, -1
+ %cond = select i1 %cmp1, i32 -1, i32 1
+ %cond2 = select i1 %cmp, i32 0, i32 %cond
+ ret i32 %cond2
+}
+
+define i32 @scmp_zero_sgt_neg(i32 %a) {
+; CHECK-LABEL: define i32 @scmp_zero_sgt_neg(
+; CHECK-SAME: i32 [[A:%.*]]) {
+; CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[A]], 0
+; CHECK-NEXT: [[CMP1:%.*]] = icmp sgt i32 [[A]], 1
+; CHECK-NEXT: [[COND:%.*]] = select i1 [[CMP1]], i32 1, i32 -1
+; CHECK-NEXT: [[COND2:%.*]] = select i1 [[CMP]], i32 0, i32 [[COND]]
+; CHECK-NEXT: ret i32 [[COND2]]
+;
+ %cmp = icmp eq i32 %a, 0
+ %cmp1 = icmp sgt i32 %a, 1
+ %cond = select i1 %cmp1, i32 1, i32 -1
+ %cond2 = select i1 %cmp, i32 0, i32 %cond
+ ret i32 %cond2
+}
+
+define i32 @ucmp_ugt_ult_neg(i32 %a) {
+; CHECK-LABEL: define i32 @ucmp_ugt_ult_neg(
+; CHECK-SAME: i32 [[A:%.*]]) {
+; CHECK-NEXT: [[CMP_NOT:%.*]] = icmp ne i32 [[A]], 0
+; CHECK-NEXT: [[RETVAL_0:%.*]] = zext i1 [[CMP_NOT]] to i32
+; CHECK-NEXT: ret i32 [[RETVAL_0]]
+;
+ %cmp = icmp ugt i32 %a, 0
+ %cmp1 = icmp ult i32 %a, 0
+ %. = select i1 %cmp1, i32 -1, i32 0
+ %retval.0 = select i1 %cmp, i32 1, i32 %.
+ ret i32 %retval.0
+}
+
+define i32 @ucmp_zero_ult_neg(i32 %a) {
+; CHECK-LABEL: define i32 @ucmp_zero_ult_neg(
+; CHECK-SAME: i32 [[A:%.*]]) {
+; CHECK-NEXT: [[CMP:%.*]] = icmp ne i32 [[A]], 0
+; CHECK-NEXT: [[RETVAL_0:%.*]] = zext i1 [[CMP]] to i32
+; CHECK-NEXT: ret i32 [[RETVAL_0]]
+;
+ %cmp = icmp eq i32 %a, 0
+ %cmp1.inv = icmp ult i32 %a, 1
+ %. = select i1 %cmp1.inv, i32 -1, i32 1
+ %retval.0 = select i1 %cmp, i32 0, i32 %.
+ ret i32 %retval.0
+}
+
+define i32 @ucmp_zero_ugt_neg(i32 %a) {
+; CHECK-LABEL: define i32 @ucmp_zero_ugt_neg(
+; CHECK-SAME: i32 [[A:%.*]]) {
+; CHECK-NEXT: [[CMP:%.*]] = icmp ne i32 [[A]], 0
+; CHECK-NEXT: [[RETVAL_0:%.*]] = sext i1 [[CMP]] to i32
+; CHECK-NEXT: ret i32 [[RETVAL_0]]
+;
+ %cmp = icmp eq i32 %a, 0
+ %cmp1.inv = icmp ugt i32 %a, -1
+ %. = select i1 %cmp1.inv, i32 1, i32 -1
+ %retval.0 = select i1 %cmp, i32 0, i32 %.
+ ret i32 %retval.0
+}
+
define i32 @scmp_sgt_slt_ab(i32 %a, i32 %b) {
; CHECK-LABEL: define i32 @scmp_sgt_slt_ab(
; CHECK-SAME: i32 [[A:%.*]], i32 [[B:%.*]]) {
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