[llvm] [InstCombine] Extend `foldSelectInstWithICmpConst` to handle minmax (PR #125346)
Yingwei Zheng via llvm-commits
llvm-commits at lists.llvm.org
Sat Feb 1 07:20:46 PST 2025
https://github.com/dtcxzyw created https://github.com/llvm/llvm-project/pull/125346
This patch extends https://github.com/llvm/llvm-project/commit/f6bb156fb10cd83953a34f75b78835cdf399ee8b to handle minmax intrinsics.
Motivating case: https://alive2.llvm.org/ce/z/JFKbYn
Addresses a regression caused by https://github.com/llvm/llvm-project/pull/121958.
>From c1645add10b225c184315196c29642ce3afcb624 Mon Sep 17 00:00:00 2001
From: Yingwei Zheng <dtcxzyw2333 at gmail.com>
Date: Sat, 1 Feb 2025 22:51:26 +0800
Subject: [PATCH 1/2] [InstCombine] Add pre-commit tests. NFC.
---
.../Transforms/InstCombine/select-min-max.ll | 67 +++++++++++++++++++
1 file changed, 67 insertions(+)
diff --git a/llvm/test/Transforms/InstCombine/select-min-max.ll b/llvm/test/Transforms/InstCombine/select-min-max.ll
index f13223284e6a68c..71c41eed8d23844 100644
--- a/llvm/test/Transforms/InstCombine/select-min-max.ll
+++ b/llvm/test/Transforms/InstCombine/select-min-max.ll
@@ -301,3 +301,70 @@ define i8 @not_smin_swap(i8 %i41, i8 %i43) {
%spec.select = select i1 %i44, i8 %i46, i8 0
ret i8 %spec.select
}
+
+define i8 @sel_umin_constant(i8 %x) {
+; CHECK-LABEL: @sel_umin_constant(
+; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i8 [[X:%.*]], -1
+; CHECK-NEXT: [[UMIN:%.*]] = call i8 @llvm.umin.i8(i8 [[X]], i8 16)
+; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i8 [[UMIN]], i8 16
+; CHECK-NEXT: ret i8 [[SEL]]
+;
+ %cmp = icmp sgt i8 %x, -1
+ %umin = call i8 @llvm.umin.i8(i8 %x, i8 16)
+ %sel = select i1 %cmp, i8 %umin, i8 16
+ ret i8 %sel
+}
+
+define i8 @sel_constant_smax_with_range_attr(i8 %x) {
+; CHECK-LABEL: @sel_constant_smax_with_range_attr(
+; CHECK-NEXT: [[CMP:%.*]] = icmp slt i8 [[X:%.*]], 0
+; CHECK-NEXT: [[SMAX:%.*]] = call range(i8 8, 16) i8 @llvm.smax.i8(i8 [[X]], i8 16)
+; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i8 16, i8 [[SMAX]]
+; CHECK-NEXT: ret i8 [[SEL]]
+;
+ %cmp = icmp slt i8 %x, 0
+ %smax = call range(i8 8, 16) i8 @llvm.smax.i8(i8 %x, i8 16)
+ %sel = select i1 %cmp, i8 16, i8 %smax
+ ret i8 %sel
+}
+
+; Negative tests
+
+define i8 @sel_umin_constant_mismatch(i8 %x) {
+; CHECK-LABEL: @sel_umin_constant_mismatch(
+; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i8 [[X:%.*]], -1
+; CHECK-NEXT: [[UMIN:%.*]] = call i8 @llvm.umin.i8(i8 [[X]], i8 16)
+; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i8 [[UMIN]], i8 15
+; CHECK-NEXT: ret i8 [[SEL]]
+;
+ %cmp = icmp sgt i8 %x, -1
+ %umin = call i8 @llvm.umin.i8(i8 %x, i8 16)
+ %sel = select i1 %cmp, i8 %umin, i8 15
+ ret i8 %sel
+}
+
+define i8 @sel_umin_constant_op_mismatch(i8 %x, i8 %y) {
+; CHECK-LABEL: @sel_umin_constant_op_mismatch(
+; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i8 [[X:%.*]], -1
+; CHECK-NEXT: [[UMIN:%.*]] = call i8 @llvm.umin.i8(i8 [[Y:%.*]], i8 16)
+; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i8 [[UMIN]], i8 16
+; CHECK-NEXT: ret i8 [[SEL]]
+;
+ %cmp = icmp sgt i8 %x, -1
+ %umin = call i8 @llvm.umin.i8(i8 %y, i8 16)
+ %sel = select i1 %cmp, i8 %umin, i8 16
+ ret i8 %sel
+}
+
+define i8 @sel_umin_non_constant(i8 %x, i8 %y) {
+; CHECK-LABEL: @sel_umin_non_constant(
+; CHECK-NEXT: [[UMIN:%.*]] = call i8 @llvm.umin.i8(i8 [[X:%.*]], i8 16)
+; CHECK-NEXT: [[CMP1:%.*]] = icmp slt i8 [[X]], 0
+; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP1]], i8 [[Y:%.*]], i8 [[UMIN]]
+; CHECK-NEXT: ret i8 [[SEL]]
+;
+ %cmp = icmp sgt i8 %x, -1
+ %umin = call i8 @llvm.umin.i8(i8 %x, i8 16)
+ %sel = select i1 %cmp, i8 %umin, i8 %y
+ ret i8 %sel
+}
>From 926e610c7d44957b08aa7562db565327747a1787 Mon Sep 17 00:00:00 2001
From: Yingwei Zheng <dtcxzyw2333 at gmail.com>
Date: Sat, 1 Feb 2025 23:16:14 +0800
Subject: [PATCH 2/2] [InstCombine] Extend `foldSelectInstWithICmpConst` to
handle minmax
---
.../InstCombine/InstCombineSelect.cpp | 36 ++++++++++++-------
.../Transforms/InstCombine/select-min-max.ll | 10 ++----
2 files changed, 27 insertions(+), 19 deletions(-)
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
index 29c5cef84ccdb72..382078e85a17b6d 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
@@ -1771,26 +1771,38 @@ static Value *foldSelectInstWithICmpConst(SelectInst &SI, ICmpInst *ICI,
return Builder.CreateBinaryIntrinsic(Intrinsic::smin, V, TVal);
}
- BinaryOperator *BO;
+ // Fold icmp(X) ? f(X) : C to f(X) when f(X) is guaranteed to be equal to C
+ // for all X in the exact range of the inverse predicate.
+ Instruction *Op;
const APInt *C;
CmpInst::Predicate CPred;
- if (match(&SI, m_Select(m_Specific(ICI), m_APInt(C), m_BinOp(BO))))
+ if (match(&SI, m_Select(m_Specific(ICI), m_APInt(C), m_Instruction(Op))))
CPred = ICI->getPredicate();
- else if (match(&SI, m_Select(m_Specific(ICI), m_BinOp(BO), m_APInt(C))))
+ else if (match(&SI, m_Select(m_Specific(ICI), m_Instruction(Op), m_APInt(C))))
CPred = ICI->getInversePredicate();
else
return nullptr;
- const APInt *BinOpC;
- if (!match(BO, m_BinOp(m_Specific(V), m_APInt(BinOpC))))
- return nullptr;
-
- ConstantRange R = ConstantRange::makeExactICmpRegion(CPred, *CmpC)
- .binaryOp(BO->getOpcode(), *BinOpC);
- if (R == *C) {
- BO->dropPoisonGeneratingFlags();
- return BO;
+ ConstantRange InvDomCR = ConstantRange::makeExactICmpRegion(CPred, *CmpC);
+ const APInt *OpC;
+ if (match(Op, m_BinOp(m_Specific(V), m_APInt(OpC)))) {
+ ConstantRange R = InvDomCR.binaryOp(
+ static_cast<Instruction::BinaryOps>(Op->getOpcode()), *OpC);
+ if (R == *C) {
+ Op->dropPoisonGeneratingFlags();
+ return Op;
+ }
+ }
+ if (auto *MMI = dyn_cast<MinMaxIntrinsic>(Op);
+ MMI && MMI->getLHS() == V && match(MMI->getRHS(), m_APInt(OpC))) {
+ ConstantRange R = ConstantRange::intrinsic(MMI->getIntrinsicID(),
+ {InvDomCR, ConstantRange(*OpC)});
+ if (R == *C) {
+ MMI->dropPoisonGeneratingAnnotations();
+ return MMI;
+ }
}
+
return nullptr;
}
diff --git a/llvm/test/Transforms/InstCombine/select-min-max.ll b/llvm/test/Transforms/InstCombine/select-min-max.ll
index 71c41eed8d23844..0430fcd5ad37009 100644
--- a/llvm/test/Transforms/InstCombine/select-min-max.ll
+++ b/llvm/test/Transforms/InstCombine/select-min-max.ll
@@ -304,10 +304,8 @@ define i8 @not_smin_swap(i8 %i41, i8 %i43) {
define i8 @sel_umin_constant(i8 %x) {
; CHECK-LABEL: @sel_umin_constant(
-; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i8 [[X:%.*]], -1
-; CHECK-NEXT: [[UMIN:%.*]] = call i8 @llvm.umin.i8(i8 [[X]], i8 16)
-; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i8 [[UMIN]], i8 16
-; CHECK-NEXT: ret i8 [[SEL]]
+; CHECK-NEXT: [[UMIN:%.*]] = call i8 @llvm.umin.i8(i8 [[X:%.*]], i8 16)
+; CHECK-NEXT: ret i8 [[UMIN]]
;
%cmp = icmp sgt i8 %x, -1
%umin = call i8 @llvm.umin.i8(i8 %x, i8 16)
@@ -317,9 +315,7 @@ define i8 @sel_umin_constant(i8 %x) {
define i8 @sel_constant_smax_with_range_attr(i8 %x) {
; CHECK-LABEL: @sel_constant_smax_with_range_attr(
-; CHECK-NEXT: [[CMP:%.*]] = icmp slt i8 [[X:%.*]], 0
-; CHECK-NEXT: [[SMAX:%.*]] = call range(i8 8, 16) i8 @llvm.smax.i8(i8 [[X]], i8 16)
-; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i8 16, i8 [[SMAX]]
+; CHECK-NEXT: [[SEL:%.*]] = call i8 @llvm.smax.i8(i8 [[X:%.*]], i8 16)
; CHECK-NEXT: ret i8 [[SEL]]
;
%cmp = icmp slt i8 %x, 0
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