[llvm] 9d38eba - [InstCombine][ProfCheck] Mark unknown select profiles in sub xor fold (#191192)

[via llvm-commits]

Author: Aiden Grossman
Date: 2026-04-09T09:06:31-07:00
New Revision: 9d38eba6e73b70030518d3ed09a01bb06b36d44b

URL: https://github.com/llvm/llvm-project/commit/9d38eba6e73b70030518d3ed09a01bb06b36d44b
DIFF: https://github.com/llvm/llvm-project/commit/9d38eba6e73b70030518d3ed09a01bb06b36d44b.diff

LOG: [InstCombine][ProfCheck] Mark unknown select profiles in sub xor fold (#191192)

Mark the weights as explicitly unknown given we cannot statically infer
the weights without value profiling due to the select being synthesized
from a binary operation.

Added: 
    

Modified: 
    llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
    llvm/test/Transforms/InstCombine/sub-xor-cmp.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
index c781c6978b275..13edf36621f0f 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
@@ -2663,9 +2663,9 @@ Instruction *InstCombinerImpl::visitSub(BinaryOperator &I) {
              (C->getType()->getScalarSizeInBits() == 1);
     };
     if (m_SubXorCmp(Op0, Op1))
-      return SelectInst::Create(C, Builder.CreateNeg(X), X);
+      return createSelectInstWithUnknownProfile(C, Builder.CreateNeg(X), X);
     if (m_SubXorCmp(Op1, Op0))
-      return SelectInst::Create(C, X, Builder.CreateNeg(X));
+      return createSelectInstWithUnknownProfile(C, X, Builder.CreateNeg(X));
   }
 
   if (Instruction *R = tryFoldInstWithCtpopWithNot(&I))

diff  --git a/llvm/test/Transforms/InstCombine/sub-xor-cmp.ll b/llvm/test/Transforms/InstCombine/sub-xor-cmp.ll
index acbc29db871e8..6223e974e412c 100644
--- a/llvm/test/Transforms/InstCombine/sub-xor-cmp.ll
+++ b/llvm/test/Transforms/InstCombine/sub-xor-cmp.ll
@@ -1,11 +1,11 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 4
 ; RUN: opt < %s -passes=instcombine -S | FileCheck %s
 
-define i64 @sext_xor_sub(i64 %a, i1 %b) {
+define i64 @sext_xor_sub(i64 %a, i1 %b) !prof !0 {
 ; CHECK-LABEL: define i64 @sext_xor_sub(
-; CHECK-SAME: i64 [[A:%.*]], i1 [[B:%.*]]) {
+; CHECK-SAME: i64 [[A:%.*]], i1 [[B:%.*]]) !prof [[PROF0:![0-9]+]] {
 ; CHECK-NEXT:    [[TMP1:%.*]] = sub i64 0, [[A]]
-; CHECK-NEXT:    [[R:%.*]] = select i1 [[B]], i64 [[TMP1]], i64 [[A]]
+; CHECK-NEXT:    [[R:%.*]] = select i1 [[B]], i64 [[TMP1]], i64 [[A]], !prof [[PROF1:![0-9]+]]
 ; CHECK-NEXT:    ret i64 [[R]]
 ;
   %c = sext i1 %b to i64
@@ -27,11 +27,11 @@ define i64 @sext_xor_sub_1(i64 %a, i1 %b) {
   ret i64 %r
 }
 
-define i64 @sext_xor_sub_2(i64 %a, i1 %b) {
+define i64 @sext_xor_sub_2(i64 %a, i1 %b) !prof !0 {
 ; CHECK-LABEL: define i64 @sext_xor_sub_2(
-; CHECK-SAME: i64 [[A:%.*]], i1 [[B:%.*]]) {
+; CHECK-SAME: i64 [[A:%.*]], i1 [[B:%.*]]) !prof [[PROF0]] {
 ; CHECK-NEXT:    [[TMP1:%.*]] = sub i64 0, [[A]]
-; CHECK-NEXT:    [[R:%.*]] = select i1 [[B]], i64 [[A]], i64 [[TMP1]]
+; CHECK-NEXT:    [[R:%.*]] = select i1 [[B]], i64 [[A]], i64 [[TMP1]], !prof [[PROF1]]
 ; CHECK-NEXT:    ret i64 [[R]]
 ;
   %c = sext i1 %b to i64
@@ -201,3 +201,9 @@ define i64 @abs
diff 2(i64 %a, i64 %b) {
   %res = sub i64 %may.rev, %c.ext
   ret i64 %res
 }
+
+!0 = !{!"function_entry_count", i64 1000}
+;.
+; CHECK: [[PROF0]] = !{!"function_entry_count", i64 1000}
+; CHECK: [[PROF1]] = !{!"unknown", !"instcombine"}
+;.