[llvm] [InstCombine] Handle trunc i1 pattern in eq-of-parts fold (PR #112704)
Nikita Popov via llvm-commits
llvm-commits at lists.llvm.org
Mon Nov 25 01:36:09 PST 2024
https://github.com/nikic updated https://github.com/llvm/llvm-project/pull/112704
>From dd6eff5d59912138d07e56fc0bab66599e3fa2db Mon Sep 17 00:00:00 2001
From: Nikita Popov <npopov at redhat.com>
Date: Wed, 16 Oct 2024 17:23:32 +0200
Subject: [PATCH 1/2] [InstCombine] Handle trunc i1 pattern in eq-of-parts fold
Equality/inequality of the low bit can be represented by
`(trunc (xor x, y) to i1)`, possibly with an extra not. We have
to handle this in the eq-of-parts fold now that we no longer
canonicalize this to a masked icmp.
Proofs: https://alive2.llvm.org/ce/z/qidkzq
Fixes https://github.com/llvm/llvm-project/issues/110919.
---
.../InstCombine/InstCombineAndOrXor.cpp | 23 ++++++++++++++-----
.../InstCombine/InstCombineInternal.h | 2 +-
.../Transforms/InstCombine/eq-of-parts.ll | 11 ++-------
3 files changed, 20 insertions(+), 16 deletions(-)
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
index c6f14018a750f5..659b8b86699fa9 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -1185,14 +1185,25 @@ static Value *extractIntPart(const IntPart &P, IRBuilderBase &Builder) {
/// (icmp eq X0, Y0) & (icmp eq X1, Y1) -> icmp eq X01, Y01
/// (icmp ne X0, Y0) | (icmp ne X1, Y1) -> icmp ne X01, Y01
/// where X0, X1 and Y0, Y1 are adjacent parts extracted from an integer.
-Value *InstCombinerImpl::foldEqOfParts(ICmpInst *Cmp0, ICmpInst *Cmp1,
- bool IsAnd) {
+Value *InstCombinerImpl::foldEqOfParts(Value *Cmp0, Value *Cmp1, bool IsAnd) {
if (!Cmp0->hasOneUse() || !Cmp1->hasOneUse())
return nullptr;
CmpInst::Predicate Pred = IsAnd ? CmpInst::ICMP_EQ : CmpInst::ICMP_NE;
- auto GetMatchPart = [&](ICmpInst *Cmp,
+ auto GetMatchPart = [&](Value *CmpV,
unsigned OpNo) -> std::optional<IntPart> {
+ Value *X, *Y;
+ // icmp ne (and x, 1), (and y, 1) <=> trunc (xor x, y) to i1
+ // icmp eq (and x, 1), (and y, 1) <=> not (trunc (xor x, y) to i1)
+ if (Pred == CmpInst::ICMP_NE
+ ? match(CmpV, m_Trunc(m_Xor(m_Value(X), m_Value(Y))))
+ : match(CmpV, m_Not(m_Trunc(m_Xor(m_Value(X), m_Value(Y))))))
+ return {{OpNo == 0 ? X : Y, 0, 1}};
+
+ auto *Cmp = dyn_cast<ICmpInst>(CmpV);
+ if (!Cmp)
+ return std::nullopt;
+
if (Pred == Cmp->getPredicate())
return matchIntPart(Cmp->getOperand(OpNo));
@@ -3404,9 +3415,6 @@ Value *InstCombinerImpl::foldAndOrOfICmps(ICmpInst *LHS, ICmpInst *RHS,
return X;
}
- if (Value *X = foldEqOfParts(LHS, RHS, IsAnd))
- return X;
-
// (icmp ne A, 0) | (icmp ne B, 0) --> (icmp ne (A|B), 0)
// (icmp eq A, 0) & (icmp eq B, 0) --> (icmp eq (A|B), 0)
// TODO: Remove this and below when foldLogOpOfMaskedICmps can handle undefs.
@@ -3529,6 +3537,9 @@ Value *InstCombinerImpl::foldBooleanAndOr(Value *LHS, Value *RHS,
if (Value *Res = foldLogicOfFCmps(LHSCmp, RHSCmp, IsAnd, IsLogical))
return Res;
+ if (Value *Res = foldEqOfParts(LHS, RHS, IsAnd))
+ return Res;
+
return nullptr;
}
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineInternal.h b/llvm/lib/Transforms/InstCombine/InstCombineInternal.h
index 9588930d7658c4..0508ed48fc19c4 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineInternal.h
+++ b/llvm/lib/Transforms/InstCombine/InstCombineInternal.h
@@ -412,7 +412,7 @@ class LLVM_LIBRARY_VISIBILITY InstCombinerImpl final
bool IsAnd, bool IsLogical = false);
Value *foldXorOfICmps(ICmpInst *LHS, ICmpInst *RHS, BinaryOperator &Xor);
- Value *foldEqOfParts(ICmpInst *Cmp0, ICmpInst *Cmp1, bool IsAnd);
+ Value *foldEqOfParts(Value *Cmp0, Value *Cmp1, bool IsAnd);
Value *foldAndOrOfICmpsUsingRanges(ICmpInst *ICmp1, ICmpInst *ICmp2,
bool IsAnd);
diff --git a/llvm/test/Transforms/InstCombine/eq-of-parts.ll b/llvm/test/Transforms/InstCombine/eq-of-parts.ll
index 9494dd6bf8e5b5..d07c2e6a5be521 100644
--- a/llvm/test/Transforms/InstCombine/eq-of-parts.ll
+++ b/llvm/test/Transforms/InstCombine/eq-of-parts.ll
@@ -1441,11 +1441,7 @@ define i1 @ne_optimized_highbits_cmp_todo_overlapping(i32 %x, i32 %y) {
define i1 @and_trunc_i1(i8 %a1, i8 %a2) {
; CHECK-LABEL: @and_trunc_i1(
-; CHECK-NEXT: [[XOR:%.*]] = xor i8 [[A1:%.*]], [[A2:%.*]]
-; CHECK-NEXT: [[CMP:%.*]] = icmp ult i8 [[XOR]], 2
-; CHECK-NEXT: [[LOBIT:%.*]] = trunc i8 [[XOR]] to i1
-; CHECK-NEXT: [[LOBIT_INV:%.*]] = xor i1 [[LOBIT]], true
-; CHECK-NEXT: [[AND:%.*]] = and i1 [[CMP]], [[LOBIT_INV]]
+; CHECK-NEXT: [[AND:%.*]] = icmp eq i8 [[A1:%.*]], [[A2:%.*]]
; CHECK-NEXT: ret i1 [[AND]]
;
%xor = xor i8 %a1, %a2
@@ -1494,10 +1490,7 @@ define i1 @and_trunc_i1_wrong_operands(i8 %a1, i8 %a2, i8 %a3) {
define i1 @or_trunc_i1(i64 %a1, i64 %a2) {
; CHECK-LABEL: @or_trunc_i1(
-; CHECK-NEXT: [[XOR:%.*]] = xor i64 [[A2:%.*]], [[A1:%.*]]
-; CHECK-NEXT: [[CMP:%.*]] = icmp ugt i64 [[XOR]], 1
-; CHECK-NEXT: [[TRUNC:%.*]] = trunc i64 [[XOR]] to i1
-; CHECK-NEXT: [[OR:%.*]] = or i1 [[CMP]], [[TRUNC]]
+; CHECK-NEXT: [[OR:%.*]] = icmp ne i64 [[A2:%.*]], [[A1:%.*]]
; CHECK-NEXT: ret i1 [[OR]]
;
%xor = xor i64 %a2, %a1
>From 7117fbbec6abb882c415c5570c135b98eb9fe8bd Mon Sep 17 00:00:00 2001
From: Nikita Popov <npopov at redhat.com>
Date: Mon, 25 Nov 2024 10:35:50 +0100
Subject: [PATCH 2/2] add assert
---
llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp | 2 ++
1 file changed, 2 insertions(+)
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
index 659b8b86699fa9..b4033fc2a418a1 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -1192,6 +1192,8 @@ Value *InstCombinerImpl::foldEqOfParts(Value *Cmp0, Value *Cmp1, bool IsAnd) {
CmpInst::Predicate Pred = IsAnd ? CmpInst::ICMP_EQ : CmpInst::ICMP_NE;
auto GetMatchPart = [&](Value *CmpV,
unsigned OpNo) -> std::optional<IntPart> {
+ assert(CmpV->getType()->isIntOrIntVectorTy(1) && "Must be bool");
+
Value *X, *Y;
// icmp ne (and x, 1), (and y, 1) <=> trunc (xor x, y) to i1
// icmp eq (and x, 1), (and y, 1) <=> not (trunc (xor x, y) to i1)
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