[llvm] Allow folding icmp eq (add X, C2), C when there is more than one-use when we can compute the range (PR #144566)
via llvm-commits
llvm-commits at lists.llvm.org
Tue Jun 17 15:19:52 PDT 2025
https://github.com/AZero13 updated https://github.com/llvm/llvm-project/pull/144566
>From 1c0705f60e3846dded45217fe62dcf5b524bf5f0 Mon Sep 17 00:00:00 2001
From: Rose <gfunni234 at gmail.com>
Date: Tue, 17 Jun 2025 12:40:21 -0400
Subject: [PATCH 1/2] [InstCombine] Pre-commit test
---
.../Transforms/InstCombine/saturating-add-sub.ll | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/llvm/test/Transforms/InstCombine/saturating-add-sub.ll b/llvm/test/Transforms/InstCombine/saturating-add-sub.ll
index cfd679c0cc592..b3bad2f88288a 100644
--- a/llvm/test/Transforms/InstCombine/saturating-add-sub.ll
+++ b/llvm/test/Transforms/InstCombine/saturating-add-sub.ll
@@ -2350,4 +2350,17 @@ define i8 @fold_add_umax_to_usub_multiuse(i8 %a) {
ret i8 %sel
}
+define i32 @add_check_zero(i32 %num) {
+; CHECK-LABEL: @add_check_zero(
+; CHECK-NEXT: [[ADD:%.*]] = add i32 [[NUM:%.*]], 1
+; CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[ADD]], 0
+; CHECK-NEXT: [[COND:%.*]] = select i1 [[CMP]], i32 -1, i32 [[ADD]]
+; CHECK-NEXT: ret i32 [[COND]]
+;
+ %add = add i32 %num, 1
+ %cmp = icmp eq i32 %add, 0
+ %cond = select i1 %cmp, i32 -1, i32 %add
+ ret i32 %cond
+}
+
declare void @usei8(i8)
>From 12e1f4098d639c1798bb48df23ce7b7991e14e75 Mon Sep 17 00:00:00 2001
From: Rose <gfunni234 at gmail.com>
Date: Tue, 17 Jun 2025 13:01:36 -0400
Subject: [PATCH 2/2] Allow folding icmp eq (add X, C2), C when there is more
than one-use when we can compute the range
If there are multiple uses of an add, we can fold a comparison anyway if we can compute a constant range for it, which should happen in cases such as saturated add.
---
.../InstCombine/InstCombineCompares.cpp | 10 +++--
.../Analysis/ValueTracking/phi-known-bits.ll | 2 +-
.../InstCombine/saturating-add-sub.ll | 4 +-
llvm/test/Transforms/InstCombine/uaddo.ll | 2 +-
.../Transforms/LoopVectorize/induction.ll | 8 ++--
...n-of-loops-that-became-side-effect-free.ll | 37 ++++---------------
6 files changed, 22 insertions(+), 41 deletions(-)
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
index 084e7fbaa268a..abad4e0059481 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -3160,7 +3160,7 @@ Instruction *InstCombinerImpl::foldICmpAddConstant(ICmpInst &Cmp,
return replaceInstUsesWith(Cmp, Cond);
}
const APInt *C2;
- if (Cmp.isEquality() || !match(Y, m_APInt(C2)))
+ if (!match(Y, m_APInt(C2)))
return nullptr;
// Fold icmp pred (add X, C2), C.
@@ -3184,8 +3184,9 @@ Instruction *InstCombinerImpl::foldICmpAddConstant(ICmpInst &Cmp,
return new ICmpInst(Pred, X, ConstantInt::get(Ty, NewC));
}
- if (ICmpInst::isUnsigned(Pred) && Add->hasNoSignedWrap() &&
- C.isNonNegative() && (C - *C2).isNonNegative() &&
+ if (!Cmp.isEquality() && ICmpInst::isUnsigned(Pred) &&
+ Add->hasNoSignedWrap() && C.isNonNegative() &&
+ (C - *C2).isNonNegative() &&
computeConstantRange(X, /*ForSigned=*/true).add(*C2).isAllNonNegative())
return new ICmpInst(ICmpInst::getSignedPredicate(Pred), X,
ConstantInt::get(Ty, C - *C2));
@@ -3205,6 +3206,9 @@ Instruction *InstCombinerImpl::foldICmpAddConstant(ICmpInst &Cmp,
return new ICmpInst(ICmpInst::ICMP_UGE, X, ConstantInt::get(Ty, Lower));
}
+ if (Cmp.isEquality())
+ return nullptr;
+
// This set of folds is intentionally placed after folds that use no-wrapping
// flags because those folds are likely better for later analysis/codegen.
const APInt SMax = APInt::getSignedMaxValue(Ty->getScalarSizeInBits());
diff --git a/llvm/test/Analysis/ValueTracking/phi-known-bits.ll b/llvm/test/Analysis/ValueTracking/phi-known-bits.ll
index 436aadbc25de6..d2fa99237a4ac 100644
--- a/llvm/test/Analysis/ValueTracking/phi-known-bits.ll
+++ b/llvm/test/Analysis/ValueTracking/phi-known-bits.ll
@@ -1119,7 +1119,7 @@ define i32 @issue_124275_wrong_br_direction(i32 noundef %inp) {
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TMP0:%.*]] = xor i32 [[INP:%.*]], -2
; CHECK-NEXT: [[XOR_INP_NEG:%.*]] = add i32 [[TMP0]], 1
-; CHECK-NEXT: [[CMP_NE_NOT:%.*]] = icmp eq i32 [[XOR_INP_NEG]], 0
+; CHECK-NEXT: [[CMP_NE_NOT:%.*]] = icmp eq i32 [[INP]], 1
; CHECK-NEXT: br i1 [[CMP_NE_NOT]], label [[B1:%.*]], label [[B0:%.*]]
; CHECK: B0:
; CHECK-NEXT: [[PHI_B0:%.*]] = phi i32 [ [[PHI_B1:%.*]], [[B1]] ], [ [[XOR_INP_NEG]], [[ENTRY:%.*]] ]
diff --git a/llvm/test/Transforms/InstCombine/saturating-add-sub.ll b/llvm/test/Transforms/InstCombine/saturating-add-sub.ll
index b3bad2f88288a..cc8ed078d4229 100644
--- a/llvm/test/Transforms/InstCombine/saturating-add-sub.ll
+++ b/llvm/test/Transforms/InstCombine/saturating-add-sub.ll
@@ -2352,9 +2352,7 @@ define i8 @fold_add_umax_to_usub_multiuse(i8 %a) {
define i32 @add_check_zero(i32 %num) {
; CHECK-LABEL: @add_check_zero(
-; CHECK-NEXT: [[ADD:%.*]] = add i32 [[NUM:%.*]], 1
-; CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[ADD]], 0
-; CHECK-NEXT: [[COND:%.*]] = select i1 [[CMP]], i32 -1, i32 [[ADD]]
+; CHECK-NEXT: [[COND:%.*]] = call i32 @llvm.uadd.sat.i32(i32 [[NUM:%.*]], i32 1)
; CHECK-NEXT: ret i32 [[COND]]
;
%add = add i32 %num, 1
diff --git a/llvm/test/Transforms/InstCombine/uaddo.ll b/llvm/test/Transforms/InstCombine/uaddo.ll
index ae7a07ec8000c..89a9569bdb7c3 100644
--- a/llvm/test/Transforms/InstCombine/uaddo.ll
+++ b/llvm/test/Transforms/InstCombine/uaddo.ll
@@ -158,7 +158,7 @@ define i1 @uaddo_1(i8 %x, ptr %p) {
; CHECK-LABEL: @uaddo_1(
; CHECK-NEXT: [[A:%.*]] = add i8 [[X:%.*]], 1
; CHECK-NEXT: store i8 [[A]], ptr [[P:%.*]], align 1
-; CHECK-NEXT: [[C:%.*]] = icmp eq i8 [[A]], 0
+; CHECK-NEXT: [[C:%.*]] = icmp eq i8 [[X]], -1
; CHECK-NEXT: ret i1 [[C]]
;
%a = add i8 %x, 1
diff --git a/llvm/test/Transforms/LoopVectorize/induction.ll b/llvm/test/Transforms/LoopVectorize/induction.ll
index 5a5b06de69552..36688665f3bd3 100644
--- a/llvm/test/Transforms/LoopVectorize/induction.ll
+++ b/llvm/test/Transforms/LoopVectorize/induction.ll
@@ -3183,7 +3183,7 @@ define i32 @testoverflowcheck() {
; IND-NEXT: [[INC4_I:%.*]] = phi i8 [ [[BC_RESUME_VAL]], [[SCALAR_PH]] ], [ [[INC_I:%.*]], [[COND_END_I]] ]
; IND-NEXT: [[AND_I:%.*]] = and i32 [[BC_MERGE_RDX]], [[TMP0]]
; IND-NEXT: [[INC_I]] = add i8 [[INC4_I]], 1
-; IND-NEXT: [[TOBOOL_I:%.*]] = icmp eq i8 [[INC_I]], 0
+; IND-NEXT: [[TOBOOL_I:%.*]] = icmp eq i8 [[INC4_I]], -1
; IND-NEXT: br i1 [[TOBOOL_I]], label [[LOOPEXIT]], label [[COND_END_I]], !llvm.loop [[LOOP33:![0-9]+]]
; IND: loopexit:
; IND-NEXT: [[AND_I_LCSSA:%.*]] = phi i32 [ [[AND_I]], [[COND_END_I]] ], [ [[TMP7]], [[MIDDLE_BLOCK]] ]
@@ -3225,7 +3225,7 @@ define i32 @testoverflowcheck() {
; UNROLL-NEXT: [[INC4_I:%.*]] = phi i8 [ [[BC_RESUME_VAL]], [[SCALAR_PH]] ], [ [[INC_I:%.*]], [[COND_END_I]] ]
; UNROLL-NEXT: [[AND_I:%.*]] = and i32 [[BC_MERGE_RDX]], [[TMP0]]
; UNROLL-NEXT: [[INC_I]] = add i8 [[INC4_I]], 1
-; UNROLL-NEXT: [[TOBOOL_I:%.*]] = icmp eq i8 [[INC_I]], 0
+; UNROLL-NEXT: [[TOBOOL_I:%.*]] = icmp eq i8 [[INC4_I]], -1
; UNROLL-NEXT: br i1 [[TOBOOL_I]], label [[LOOPEXIT]], label [[COND_END_I]], !llvm.loop [[LOOP33:![0-9]+]]
; UNROLL: loopexit:
; UNROLL-NEXT: [[AND_I_LCSSA:%.*]] = phi i32 [ [[AND_I]], [[COND_END_I]] ], [ [[TMP7]], [[MIDDLE_BLOCK]] ]
@@ -3315,7 +3315,7 @@ define i32 @testoverflowcheck() {
; INTERLEAVE-NEXT: [[INC4_I:%.*]] = phi i8 [ [[BC_RESUME_VAL]], [[SCALAR_PH]] ], [ [[INC_I:%.*]], [[COND_END_I]] ]
; INTERLEAVE-NEXT: [[AND_I:%.*]] = and i32 [[BC_MERGE_RDX]], [[TMP0]]
; INTERLEAVE-NEXT: [[INC_I]] = add i8 [[INC4_I]], 1
-; INTERLEAVE-NEXT: [[TOBOOL_I:%.*]] = icmp eq i8 [[INC_I]], 0
+; INTERLEAVE-NEXT: [[TOBOOL_I:%.*]] = icmp eq i8 [[INC4_I]], -1
; INTERLEAVE-NEXT: br i1 [[TOBOOL_I]], label [[LOOPEXIT]], label [[COND_END_I]], !llvm.loop [[LOOP33:![0-9]+]]
; INTERLEAVE: loopexit:
; INTERLEAVE-NEXT: [[AND_I_LCSSA:%.*]] = phi i32 [ [[AND_I]], [[COND_END_I]] ], [ [[TMP7]], [[MIDDLE_BLOCK]] ]
@@ -5399,7 +5399,7 @@ define i32 @PR32419(i32 %a, i16 %b) {
; INTERLEAVE-NEXT: [[VAR4:%.*]] = phi i32 [ [[TMP50]], [[FOR_COND]] ], [ 0, [[FOR_BODY]] ]
; INTERLEAVE-NEXT: [[VAR6]] = or i32 [[VAR0]], [[VAR4]]
; INTERLEAVE-NEXT: [[I_NEXT]] = add nsw i32 [[I]], 1
-; INTERLEAVE-NEXT: [[COND:%.*]] = icmp eq i32 [[I_NEXT]], 0
+; INTERLEAVE-NEXT: [[COND:%.*]] = icmp eq i32 [[I]], -1
; INTERLEAVE-NEXT: br i1 [[COND]], label [[FOR_END]], label [[FOR_BODY]], !llvm.loop [[LOOP47:![0-9]+]]
; INTERLEAVE: for.end:
; INTERLEAVE-NEXT: [[VAR7:%.*]] = phi i32 [ [[VAR6]], [[FOR_INC]] ], [ poison, [[MIDDLE_BLOCK]] ]
diff --git a/llvm/test/Transforms/PhaseOrdering/deletion-of-loops-that-became-side-effect-free.ll b/llvm/test/Transforms/PhaseOrdering/deletion-of-loops-that-became-side-effect-free.ll
index 641f216302146..df78f3d8fd54a 100644
--- a/llvm/test/Transforms/PhaseOrdering/deletion-of-loops-that-became-side-effect-free.ll
+++ b/llvm/test/Transforms/PhaseOrdering/deletion-of-loops-that-became-side-effect-free.ll
@@ -96,35 +96,10 @@ while.end:
}
define dso_local zeroext i1 @is_not_empty_variant3(ptr %p) {
-; O3-LABEL: @is_not_empty_variant3(
-; O3-NEXT: entry:
-; O3-NEXT: [[TOBOOL_NOT4_I:%.*]] = icmp ne ptr [[P:%.*]], null
-; O3-NEXT: ret i1 [[TOBOOL_NOT4_I]]
-;
-; O2-LABEL: @is_not_empty_variant3(
-; O2-NEXT: entry:
-; O2-NEXT: [[TOBOOL_NOT4_I:%.*]] = icmp ne ptr [[P:%.*]], null
-; O2-NEXT: ret i1 [[TOBOOL_NOT4_I]]
-;
-; O1-LABEL: @is_not_empty_variant3(
-; O1-NEXT: entry:
-; O1-NEXT: [[TOBOOL_NOT4_I:%.*]] = icmp eq ptr [[P:%.*]], null
-; O1-NEXT: br i1 [[TOBOOL_NOT4_I]], label [[COUNT_NODES_VARIANT3_EXIT:%.*]], label [[WHILE_BODY_I:%.*]]
-; O1: while.body.i:
-; O1-NEXT: [[SIZE_06_I:%.*]] = phi i64 [ [[INC_I:%.*]], [[WHILE_BODY_I]] ], [ 0, [[ENTRY:%.*]] ]
-; O1-NEXT: [[P_ADDR_05_I:%.*]] = phi ptr [ [[TMP0:%.*]], [[WHILE_BODY_I]] ], [ [[P]], [[ENTRY]] ]
-; O1-NEXT: [[CMP_I:%.*]] = icmp ne i64 [[SIZE_06_I]], -1
-; O1-NEXT: call void @llvm.assume(i1 [[CMP_I]])
-; O1-NEXT: [[TMP0]] = load ptr, ptr [[P_ADDR_05_I]], align 8
-; O1-NEXT: [[INC_I]] = add i64 [[SIZE_06_I]], 1
-; O1-NEXT: [[TOBOOL_NOT_I:%.*]] = icmp eq ptr [[TMP0]], null
-; O1-NEXT: br i1 [[TOBOOL_NOT_I]], label [[COUNT_NODES_VARIANT3_EXIT_LOOPEXIT:%.*]], label [[WHILE_BODY_I]], !llvm.loop [[LOOP0:![0-9]+]]
-; O1: count_nodes_variant3.exit.loopexit:
-; O1-NEXT: [[PHI_CMP:%.*]] = icmp ne i64 [[INC_I]], 0
-; O1-NEXT: br label [[COUNT_NODES_VARIANT3_EXIT]]
-; O1: count_nodes_variant3.exit:
-; O1-NEXT: [[SIZE_0_LCSSA_I:%.*]] = phi i1 [ false, [[ENTRY]] ], [ [[PHI_CMP]], [[COUNT_NODES_VARIANT3_EXIT_LOOPEXIT]] ]
-; O1-NEXT: ret i1 [[SIZE_0_LCSSA_I]]
+; ALL-LABEL: @is_not_empty_variant3(
+; ALL-NEXT: entry:
+; ALL-NEXT: [[TOBOOL_NOT4_I:%.*]] = icmp ne ptr [[P:%.*]], null
+; ALL-NEXT: ret i1 [[TOBOOL_NOT4_I]]
;
entry:
%p.addr = alloca ptr, align 8
@@ -182,3 +157,7 @@ declare void @llvm.assume(i1 noundef)
!1 = !{!"llvm.loop.mustprogress"}
!2 = distinct !{!2, !1}
!3 = distinct !{!3, !1}
+;; NOTE: These prefixes are unused and the list is autogenerated. Do not add tests below this line:
+; O1: {{.*}}
+; O2: {{.*}}
+; O3: {{.*}}
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