[llvm] [AArch64] Report icmp as free if it can be folded into ands (PR #143286)
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Mon Jun 16 07:27:58 PDT 2025
https://github.com/AZero13 updated https://github.com/llvm/llvm-project/pull/143286
>From 761cd5f41a255abcdc4dc352c3750b258cf60813 Mon Sep 17 00:00:00 2001
From: Rose <gfunni234 at gmail.com>
Date: Mon, 16 Jun 2025 09:50:04 -0400
Subject: [PATCH 1/2] Pre-commit tests (NFC)
---
llvm/test/Analysis/CostModel/AArch64/cmp.ll | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)
diff --git a/llvm/test/Analysis/CostModel/AArch64/cmp.ll b/llvm/test/Analysis/CostModel/AArch64/cmp.ll
index aba113865af10..94e921e798cda 100644
--- a/llvm/test/Analysis/CostModel/AArch64/cmp.ll
+++ b/llvm/test/Analysis/CostModel/AArch64/cmp.ll
@@ -53,6 +53,14 @@ define void @andcmp() {
; CHECK-NEXT: Cost Model: Found costs of RThru:0 CodeSize:1 Lat:1 SizeLat:1 for: %c32 = icmp eq i32 %a32, 0
; CHECK-NEXT: Cost Model: Found costs of 1 for: %a64 = and i64 undef, undef
; CHECK-NEXT: Cost Model: Found costs of RThru:0 CodeSize:1 Lat:1 SizeLat:1 for: %c64 = icmp ne i64 %a64, 0
+; CHECK-NEXT: Cost Model: Found costs of 1 for: %c32ge = icmp sge i32 %a32, 1
+; CHECK-NEXT: Cost Model: Found costs of 1 for: %c32le = icmp slt i32 %a32, 1
+; CHECK-NEXT: Cost Model: Found costs of 1 for: %c32leneg = icmp sle i32 %a32, -1
+; CHECK-NEXT: Cost Model: Found costs of 1 for: %c32gtneg = icmp sgt i32 %a32, -1
+; CHECK-NEXT: Cost Model: Found costs of 1 for: %c64ge = icmp sge i64 %a64, 1
+; CHECK-NEXT: Cost Model: Found costs of 1 for: %c64le = icmp slt i64 %a64, 1
+; CHECK-NEXT: Cost Model: Found costs of 1 for: %c64leneg = icmp sle i64 %a64, -1
+; CHECK-NEXT: Cost Model: Found costs of 1 for: %c64gtneg = icmp sgt i64 %a64, -1
; CHECK-NEXT: Cost Model: Found costs of RThru:2 CodeSize:1 Lat:1 SizeLat:1 for: %a128 = and i128 undef, undef
; CHECK-NEXT: Cost Model: Found costs of RThru:2 CodeSize:1 Lat:1 SizeLat:1 for: %c128 = icmp eq i128 %a128, 0
; CHECK-NEXT: Cost Model: Found costs of 1 for: %av16i8 = and <16 x i8> undef, undef
@@ -73,6 +81,17 @@ define void @andcmp() {
%c32 = icmp eq i32 %a32, 0
%a64 = and i64 undef, undef
%c64 = icmp ne i64 %a64, 0
+
+ %c32ge = icmp sge i32 %a32, 1
+ %c32le = icmp slt i32 %a32, 1
+ %c32leneg = icmp sle i32 %a32, -1
+ %c32gtneg = icmp sgt i32 %a32, -1
+
+ %c64ge = icmp sge i64 %a64, 1
+ %c64le = icmp slt i64 %a64, 1
+ %c64leneg = icmp sle i64 %a64, -1
+ %c64gtneg = icmp sgt i64 %a64, -1
+
%a128 = and i128 undef, undef
%c128 = icmp eq i128 %a128, zeroinitializer
%av16i8 = and <16 x i8> undef, undef
>From be7cceddc20408febb2accb958fbcab23068aa9e Mon Sep 17 00:00:00 2001
From: Rose <gfunni234 at gmail.com>
Date: Mon, 16 Jun 2025 09:50:35 -0400
Subject: [PATCH 2/2] [AArch64] Report icmp as free if it can be folded into
ands
Since changing the backend to fold x >= 1 / x < 1 -> x > 0 / x <= 0 and x <= -1 / x > -1 -> x > 0 / x <= 0, this should be reflected in the cost.
---
.../AArch64/AArch64TargetTransformInfo.cpp | 25 +++++++++++++------
llvm/test/Analysis/CostModel/AArch64/cmp.ll | 18 ++++++-------
2 files changed, 27 insertions(+), 16 deletions(-)
diff --git a/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp b/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
index 0232ac421aeda..ed051f295752e 100644
--- a/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
+++ b/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
@@ -4353,15 +4353,26 @@ InstructionCost AArch64TTIImpl::getCmpSelInstrCost(
}
}
- // Treat the icmp in icmp(and, 0) as free, as we can make use of ands.
- // FIXME: This can apply to more conditions and add/sub if it can be shown to
- // be profitable.
+ // Treat the icmp in icmp(and, 0) or icmp(and, -1/1) when it can be folded to
+ // icmp(and, 0) as free, as we can make use of ands, but only if the
+ // comparison is not unsigned.
if (ValTy->isIntegerTy() && ISD == ISD::SETCC && I &&
- ICmpInst::isEquality(VecPred) &&
+ !CmpInst::isUnsigned(VecPred) &&
TLI->isTypeLegal(TLI->getValueType(DL, ValTy)) &&
- match(I->getOperand(1), m_Zero()) &&
- match(I->getOperand(0), m_And(m_Value(), m_Value())))
- return 0;
+ match(I->getOperand(0), m_And(m_Value(), m_Value()))) {
+ if (match(I->getOperand(1), m_Zero()))
+ return 0;
+
+ // x >= 1 / x < 1 -> x > 0 / x <= 0
+ if (match(I->getOperand(1), m_One()) &&
+ (VecPred == CmpInst::ICMP_SLT || VecPred == CmpInst::ICMP_SGE))
+ return 0;
+
+ // x <= -1 / x > -1 -> x > 0 / x <= 0
+ if (match(I->getOperand(1), m_AllOnes()) &&
+ (VecPred == CmpInst::ICMP_SLE || VecPred == CmpInst::ICMP_SGT))
+ return 0;
+ }
// The base case handles scalable vectors fine for now, since it treats the
// cost as 1 * legalization cost.
diff --git a/llvm/test/Analysis/CostModel/AArch64/cmp.ll b/llvm/test/Analysis/CostModel/AArch64/cmp.ll
index 94e921e798cda..16b3913f52028 100644
--- a/llvm/test/Analysis/CostModel/AArch64/cmp.ll
+++ b/llvm/test/Analysis/CostModel/AArch64/cmp.ll
@@ -53,14 +53,14 @@ define void @andcmp() {
; CHECK-NEXT: Cost Model: Found costs of RThru:0 CodeSize:1 Lat:1 SizeLat:1 for: %c32 = icmp eq i32 %a32, 0
; CHECK-NEXT: Cost Model: Found costs of 1 for: %a64 = and i64 undef, undef
; CHECK-NEXT: Cost Model: Found costs of RThru:0 CodeSize:1 Lat:1 SizeLat:1 for: %c64 = icmp ne i64 %a64, 0
-; CHECK-NEXT: Cost Model: Found costs of 1 for: %c32ge = icmp sge i32 %a32, 1
-; CHECK-NEXT: Cost Model: Found costs of 1 for: %c32le = icmp slt i32 %a32, 1
-; CHECK-NEXT: Cost Model: Found costs of 1 for: %c32leneg = icmp sle i32 %a32, -1
-; CHECK-NEXT: Cost Model: Found costs of 1 for: %c32gtneg = icmp sgt i32 %a32, -1
-; CHECK-NEXT: Cost Model: Found costs of 1 for: %c64ge = icmp sge i64 %a64, 1
-; CHECK-NEXT: Cost Model: Found costs of 1 for: %c64le = icmp slt i64 %a64, 1
-; CHECK-NEXT: Cost Model: Found costs of 1 for: %c64leneg = icmp sle i64 %a64, -1
-; CHECK-NEXT: Cost Model: Found costs of 1 for: %c64gtneg = icmp sgt i64 %a64, -1
+; CHECK-NEXT: Cost Model: Found costs of RThru:0 CodeSize:1 Lat:1 SizeLat:1 for: %c32ge = icmp sge i32 %a32, 1
+; CHECK-NEXT: Cost Model: Found costs of RThru:0 CodeSize:1 Lat:1 SizeLat:1 for: %c32le = icmp slt i32 %a32, 1
+; CHECK-NEXT: Cost Model: Found costs of RThru:0 CodeSize:1 Lat:1 SizeLat:1 for: %c32leneg = icmp sle i32 %a32, -1
+; CHECK-NEXT: Cost Model: Found costs of RThru:0 CodeSize:1 Lat:1 SizeLat:1 for: %c32gtneg = icmp sgt i32 %a32, -1
+; CHECK-NEXT: Cost Model: Found costs of RThru:0 CodeSize:1 Lat:1 SizeLat:1 for: %c64ge = icmp sge i64 %a64, 1
+; CHECK-NEXT: Cost Model: Found costs of RThru:0 CodeSize:1 Lat:1 SizeLat:1 for: %c64le = icmp slt i64 %a64, 1
+; CHECK-NEXT: Cost Model: Found costs of RThru:0 CodeSize:1 Lat:1 SizeLat:1 for: %c64leneg = icmp sle i64 %a64, -1
+; CHECK-NEXT: Cost Model: Found costs of RThru:0 CodeSize:1 Lat:1 SizeLat:1 for: %c64gtneg = icmp sgt i64 %a64, -1
; CHECK-NEXT: Cost Model: Found costs of RThru:2 CodeSize:1 Lat:1 SizeLat:1 for: %a128 = and i128 undef, undef
; CHECK-NEXT: Cost Model: Found costs of RThru:2 CodeSize:1 Lat:1 SizeLat:1 for: %c128 = icmp eq i128 %a128, 0
; CHECK-NEXT: Cost Model: Found costs of 1 for: %av16i8 = and <16 x i8> undef, undef
@@ -70,7 +70,7 @@ define void @andcmp() {
; CHECK-NEXT: Cost Model: Found costs of 1 for: %av4i32 = and <4 x i32> undef, undef
; CHECK-NEXT: Cost Model: Found costs of 1 for: %cv4i32 = icmp ne <4 x i32> %av4i32, zeroinitializer
; CHECK-NEXT: Cost Model: Found costs of 1 for: %c32not0 = icmp eq i32 %a32, 1
-; CHECK-NEXT: Cost Model: Found costs of 1 for: %c64sle = icmp sle i64 %a64, 0
+; CHECK-NEXT: Cost Model: Found costs of RThru:0 CodeSize:1 Lat:1 SizeLat:1 for: %c64sle = icmp sle i64 %a64, 0
; CHECK-NEXT: Cost Model: Found costs of RThru:0 CodeSize:1 Lat:1 SizeLat:1 for: ret void
;
%a8 = and i8 undef, undef
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