[llvm] Reland [InstCombine] Teach foldSelectOpOp about samesign (PR #124320)
Ramkumar Ramachandra via llvm-commits
llvm-commits at lists.llvm.org
Fri Jan 24 10:17:03 PST 2025
https://github.com/artagnon updated https://github.com/llvm/llvm-project/pull/124320
>From 6e8034bcbc69b04e85617b0d6ec996f9ce87c41f Mon Sep 17 00:00:00 2001
From: Ramkumar Ramachandra <ramkumar.ramachandra at codasip.com>
Date: Tue, 14 Jan 2025 19:58:17 +0000
Subject: [PATCH] Reland [InstCombine] Teach foldSelectOpOp about samesign
Changes: There was a serious bug in the previous patch, leading to a
miscompile. See #122723 for the miscompile report from Alexander, and
the follow-up investigation by Nikita. The patch has since been
reworked, and now includes the testcase from the miscompile.
Follow up on 4a0d53a (PatternMatch: migrate to CmpPredicate) to get rid
of one of the FIXMEs it introduced by replacing a predicate comparison
with CmpPredicate::getMatching.
Co-authored-by: Nikita Popov <npopov at redhat.com>
---
.../InstCombine/InstCombineSelect.cpp | 14 ++-
.../test/Transforms/InstCombine/select-cmp.ll | 108 ++++++++++++++++++
2 files changed, 116 insertions(+), 6 deletions(-)
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
index f66a976ccb47fe..4c78c0e74d3f45 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
@@ -428,16 +428,18 @@ Instruction *InstCombinerImpl::foldSelectOpOp(SelectInst &SI, Instruction *TI,
CmpPredicate TPred, FPred;
if (match(TI, m_ICmp(TPred, m_Value(), m_Value())) &&
match(FI, m_ICmp(FPred, m_Value(), m_Value()))) {
- // FIXME: Use CmpPredicate::getMatching here.
- CmpInst::Predicate T = TPred, F = FPred;
- if (T == F || T == ICmpInst::getSwappedCmpPredicate(F)) {
- bool Swapped = T != F;
+ auto P = CmpPredicate::getMatching(TPred, FPred);
+ bool Swapped = !P;
+ if (Swapped)
+ P = CmpPredicate::getMatching(TPred,
+ ICmpInst::getSwappedCmpPredicate(FPred));
+ if (P) {
if (Value *MatchOp =
- getCommonOp(TI, FI, ICmpInst::isEquality(TPred), Swapped)) {
+ getCommonOp(TI, FI, ICmpInst::isEquality(*P), Swapped)) {
Value *NewSel = Builder.CreateSelect(Cond, OtherOpT, OtherOpF,
SI.getName() + ".v", &SI);
return new ICmpInst(
- MatchIsOpZero ? TPred : ICmpInst::getSwappedCmpPredicate(TPred),
+ MatchIsOpZero ? *P : ICmpInst::getSwappedCmpPredicate(*P),
MatchOp, NewSel);
}
}
diff --git a/llvm/test/Transforms/InstCombine/select-cmp.ll b/llvm/test/Transforms/InstCombine/select-cmp.ll
index f7505bd85f89eb..b1bd7a0ecc8ac6 100644
--- a/llvm/test/Transforms/InstCombine/select-cmp.ll
+++ b/llvm/test/Transforms/InstCombine/select-cmp.ll
@@ -23,6 +23,18 @@ define i1 @icmp_ne_common_op00(i1 %c, i6 %x, i6 %y, i6 %z) {
ret i1 %r
}
+define i1 @icmp_ne_samesign_common(i1 %c, i6 %x, i6 %y, i6 %z) {
+; CHECK-LABEL: @icmp_ne_samesign_common(
+; CHECK-NEXT: [[R_V:%.*]] = select i1 [[C:%.*]], i6 [[Y:%.*]], i6 [[Z:%.*]]
+; CHECK-NEXT: [[R:%.*]] = icmp ne i6 [[X:%.*]], [[R_V]]
+; CHECK-NEXT: ret i1 [[R]]
+;
+ %cmp1 = icmp samesign ne i6 %x, %y
+ %cmp2 = icmp ne i6 %x, %z
+ %r = select i1 %c, i1 %cmp1, i1 %cmp2
+ ret i1 %r
+}
+
define i1 @icmp_ne_common_op01(i1 %c, i3 %x, i3 %y, i3 %z) {
; CHECK-LABEL: @icmp_ne_common_op01(
; CHECK-NEXT: [[R_V:%.*]] = select i1 [[C:%.*]], i3 [[Y:%.*]], i3 [[Z:%.*]]
@@ -71,6 +83,18 @@ define i1 @icmp_eq_common_op00(i1 %c, i5 %x, i5 %y, i5 %z) {
ret i1 %r
}
+define i1 @icmp_eq_samesign_common(i1 %c, i5 %x, i5 %y, i5 %z) {
+; CHECK-LABEL: @icmp_eq_samesign_common(
+; CHECK-NEXT: [[R_V:%.*]] = select i1 [[C:%.*]], i5 [[Y:%.*]], i5 [[Z:%.*]]
+; CHECK-NEXT: [[R:%.*]] = icmp eq i5 [[X:%.*]], [[R_V]]
+; CHECK-NEXT: ret i1 [[R]]
+;
+ %cmp1 = icmp eq i5 %x, %y
+ %cmp2 = icmp samesign eq i5 %x, %z
+ %r = select i1 %c, i1 %cmp1, i1 %cmp2
+ ret i1 %r
+}
+
define <5 x i1> @icmp_eq_common_op01(<5 x i1> %c, <5 x i7> %x, <5 x i7> %y, <5 x i7> %z) {
; CHECK-LABEL: @icmp_eq_common_op01(
; CHECK-NEXT: [[R_V:%.*]] = select <5 x i1> [[C:%.*]], <5 x i7> [[Y:%.*]], <5 x i7> [[Z:%.*]]
@@ -134,6 +158,18 @@ define i1 @icmp_slt_common(i1 %c, i6 %x, i6 %y, i6 %z) {
ret i1 %r
}
+define i1 @icmp_slt_samesign_common(i1 %c, i6 %x, i6 %y, i6 %z) {
+; CHECK-LABEL: @icmp_slt_samesign_common(
+; CHECK-NEXT: [[R_V:%.*]] = select i1 [[C:%.*]], i6 [[Y:%.*]], i6 [[Z:%.*]]
+; CHECK-NEXT: [[R:%.*]] = icmp slt i6 [[X:%.*]], [[R_V]]
+; CHECK-NEXT: ret i1 [[R]]
+;
+ %cmp1 = icmp samesign ult i6 %x, %y
+ %cmp2 = icmp slt i6 %x, %z
+ %r = select i1 %c, i1 %cmp1, i1 %cmp2
+ ret i1 %r
+}
+
define i1 @icmp_sgt_common(i1 %c, i6 %x, i6 %y, i6 %z) {
; CHECK-LABEL: @icmp_sgt_common(
; CHECK-NEXT: [[R_V:%.*]] = select i1 [[C:%.*]], i6 [[Y:%.*]], i6 [[Z:%.*]]
@@ -146,6 +182,18 @@ define i1 @icmp_sgt_common(i1 %c, i6 %x, i6 %y, i6 %z) {
ret i1 %r
}
+define i1 @icmp_sgt_samesign_common(i1 %c, i6 %x, i6 %y, i6 %z) {
+; CHECK-LABEL: @icmp_sgt_samesign_common(
+; CHECK-NEXT: [[R_V:%.*]] = select i1 [[C:%.*]], i6 [[Y:%.*]], i6 [[Z:%.*]]
+; CHECK-NEXT: [[R:%.*]] = icmp sgt i6 [[X:%.*]], [[R_V]]
+; CHECK-NEXT: ret i1 [[R]]
+;
+ %cmp1 = icmp samesign ugt i6 %x, %y
+ %cmp2 = icmp sgt i6 %x, %z
+ %r = select i1 %c, i1 %cmp1, i1 %cmp2
+ ret i1 %r
+}
+
define i1 @icmp_sle_common(i1 %c, i6 %x, i6 %y, i6 %z) {
; CHECK-LABEL: @icmp_sle_common(
; CHECK-NEXT: [[R_V:%.*]] = select i1 [[C:%.*]], i6 [[Y:%.*]], i6 [[Z:%.*]]
@@ -158,6 +206,18 @@ define i1 @icmp_sle_common(i1 %c, i6 %x, i6 %y, i6 %z) {
ret i1 %r
}
+define i1 @icmp_sle_samesign_common(i1 %c, i6 %x, i6 %y, i6 %z) {
+; CHECK-LABEL: @icmp_sle_samesign_common(
+; CHECK-NEXT: [[R_V:%.*]] = select i1 [[C:%.*]], i6 [[Y:%.*]], i6 [[Z:%.*]]
+; CHECK-NEXT: [[R:%.*]] = icmp sge i6 [[X:%.*]], [[R_V]]
+; CHECK-NEXT: ret i1 [[R]]
+;
+ %cmp1 = icmp sle i6 %y, %x
+ %cmp2 = icmp samesign ule i6 %z, %x
+ %r = select i1 %c, i1 %cmp1, i1 %cmp2
+ ret i1 %r
+}
+
define i1 @icmp_sge_common(i1 %c, i6 %x, i6 %y, i6 %z) {
; CHECK-LABEL: @icmp_sge_common(
; CHECK-NEXT: [[R_V:%.*]] = select i1 [[C:%.*]], i6 [[Y:%.*]], i6 [[Z:%.*]]
@@ -170,6 +230,18 @@ define i1 @icmp_sge_common(i1 %c, i6 %x, i6 %y, i6 %z) {
ret i1 %r
}
+define i1 @icmp_sge_samesign_common(i1 %c, i6 %x, i6 %y, i6 %z) {
+; CHECK-LABEL: @icmp_sge_samesign_common(
+; CHECK-NEXT: [[R_V:%.*]] = select i1 [[C:%.*]], i6 [[Y:%.*]], i6 [[Z:%.*]]
+; CHECK-NEXT: [[R:%.*]] = icmp sle i6 [[X:%.*]], [[R_V]]
+; CHECK-NEXT: ret i1 [[R]]
+;
+ %cmp1 = icmp sge i6 %y, %x
+ %cmp2 = icmp samesign uge i6 %z, %x
+ %r = select i1 %c, i1 %cmp1, i1 %cmp2
+ ret i1 %r
+}
+
define i1 @icmp_slt_sgt_common(i1 %c, i6 %x, i6 %y, i6 %z) {
; CHECK-LABEL: @icmp_slt_sgt_common(
; CHECK-NEXT: [[R_V:%.*]] = select i1 [[C:%.*]], i6 [[Y:%.*]], i6 [[Z:%.*]]
@@ -182,6 +254,18 @@ define i1 @icmp_slt_sgt_common(i1 %c, i6 %x, i6 %y, i6 %z) {
ret i1 %r
}
+define i1 @icmp_slt_sgt_samesign_common(i1 %c, i6 %x, i6 %y, i6 %z) {
+; CHECK-LABEL: @icmp_slt_sgt_samesign_common(
+; CHECK-NEXT: [[R_V:%.*]] = select i1 [[C:%.*]], i6 [[Y:%.*]], i6 [[Z:%.*]]
+; CHECK-NEXT: [[R:%.*]] = icmp slt i6 [[X:%.*]], [[R_V]]
+; CHECK-NEXT: ret i1 [[R]]
+;
+ %cmp1 = icmp samesign ult i6 %x, %y
+ %cmp2 = icmp sgt i6 %z, %x
+ %r = select i1 %c, i1 %cmp1, i1 %cmp2
+ ret i1 %r
+}
+
define i1 @icmp_sle_sge_common(i1 %c, i6 %x, i6 %y, i6 %z) {
; CHECK-LABEL: @icmp_sle_sge_common(
; CHECK-NEXT: [[R_V:%.*]] = select i1 [[C:%.*]], i6 [[Y:%.*]], i6 [[Z:%.*]]
@@ -194,6 +278,18 @@ define i1 @icmp_sle_sge_common(i1 %c, i6 %x, i6 %y, i6 %z) {
ret i1 %r
}
+define i1 @icmp_sle_sge_samesign_common(i1 %c, i6 %x, i6 %y, i6 %z) {
+; CHECK-LABEL: @icmp_sle_sge_samesign_common(
+; CHECK-NEXT: [[R_V:%.*]] = select i1 [[C:%.*]], i6 [[Y:%.*]], i6 [[Z:%.*]]
+; CHECK-NEXT: [[R:%.*]] = icmp sge i6 [[X:%.*]], [[R_V]]
+; CHECK-NEXT: ret i1 [[R]]
+;
+ %cmp1 = icmp sle i6 %y, %x
+ %cmp2 = icmp samesign uge i6 %x, %z
+ %r = select i1 %c, i1 %cmp1, i1 %cmp2
+ ret i1 %r
+}
+
define i1 @icmp_ult_common(i1 %c, i6 %x, i6 %y, i6 %z) {
; CHECK-LABEL: @icmp_ult_common(
; CHECK-NEXT: [[R_V:%.*]] = select i1 [[C:%.*]], i6 [[Y:%.*]], i6 [[Z:%.*]]
@@ -700,5 +796,17 @@ define i1 @sel_icmp_cmp_and_no_simplify_comm(i1 %c, i32 %a1, i32 %a2, i8 %b) {
ret i1 %cmp
}
+define i1 @icmp_lt_slt(i1 %c, i32 %arg) {
+; CHECK-LABEL: @icmp_lt_slt(
+; CHECK-NEXT: [[SELECT_V:%.*]] = select i1 [[C:%.*]], i32 131072, i32 0
+; CHECK-NEXT: [[SELECT:%.*]] = icmp slt i32 [[ARG:%.*]], [[SELECT_V]]
+; CHECK-NEXT: ret i1 [[SELECT]]
+;
+ %cmp1 = icmp samesign ult i32 %arg, 131072
+ %cmp2 = icmp slt i32 %arg, 0
+ %select = select i1 %c, i1 %cmp1, i1 %cmp2
+ ret i1 %select
+}
+
declare void @use(i1)
declare void @use.i8(i8)
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