[llvm] [profcheck] Propagate profile metadata in trunc(select) transform (PR #162406)

[Jin Huang via llvm-commits]

https://github.com/jinhuang1102 updated https://github.com/llvm/llvm-project/pull/162406

>From 9a109b549369330a1547be58e10a95a697bb2294 Mon Sep 17 00:00:00 2001
From: Jin Huang <jingold at google.com>
Date: Wed, 8 Oct 2025 00:07:00 +0000
Subject: [PATCH 1/2] Fix the no prof metadata on select after trunc(select).

---
 .../AggressiveInstCombine/TruncInstCombine.cpp           | 2 +-
 .../Transforms/AggressiveInstCombine/trunc_select.ll     | 9 +++++++--
 .../Transforms/AggressiveInstCombine/trunc_select_cmp.ll | 8 ++++++--
 3 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/llvm/lib/Transforms/AggressiveInstCombine/TruncInstCombine.cpp b/llvm/lib/Transforms/AggressiveInstCombine/TruncInstCombine.cpp
index 9b9e2bac5db32..38f3a81bc2c99 100644
--- a/llvm/lib/Transforms/AggressiveInstCombine/TruncInstCombine.cpp
+++ b/llvm/lib/Transforms/AggressiveInstCombine/TruncInstCombine.cpp
@@ -459,7 +459,7 @@ void TruncInstCombine::ReduceExpressionGraph(Type *SclTy) {
       Value *Op0 = I->getOperand(0);
       Value *LHS = getReducedOperand(I->getOperand(1), SclTy);
       Value *RHS = getReducedOperand(I->getOperand(2), SclTy);
-      Res = Builder.CreateSelect(Op0, LHS, RHS);
+      Res = Builder.CreateSelect(Op0, LHS, RHS, "select", I);
       break;
     }
     case Instruction::PHI: {
diff --git a/llvm/test/Transforms/AggressiveInstCombine/trunc_select.ll b/llvm/test/Transforms/AggressiveInstCombine/trunc_select.ll
index fb147821889db..12da17abcfdd4 100644
--- a/llvm/test/Transforms/AggressiveInstCombine/trunc_select.ll
+++ b/llvm/test/Transforms/AggressiveInstCombine/trunc_select.ll
@@ -3,10 +3,11 @@
 
 target datalayout = "e-m:m-p1:64:64:64-p:32:32:32-n8:16:32"
 
-define dso_local i16 @select_i16(i16 %a, i16 %b, i1 %cond) {
+define dso_local i16 @select_i16(i16 %a, i16 %b, i1 %cond) !prof !0 {
 ; CHECK-LABEL: @select_i16(
+; CHECK: !prof [[PROF_0:![0-9]+]] {
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[SEL:%.*]] = select i1 [[COND:%.*]], i16 [[A:%.*]], i16 [[B:%.*]]
+; CHECK-NEXT:    [[SEL:%.*]] = select i1 [[COND:%.*]], i16 [[A:%.*]], i16 [[B:%.*]], !prof [[PROF_1:![0-9]+]]
 ; CHECK-NEXT:    ret i16 [[SEL]]
 ;
 entry:
@@ -134,3 +135,7 @@ entry:
   ret i16 %conv4
 }
 
+!0 = !{!"function_entry_count", i64 1000}
+; CHECK: [[PROF_0]] = !{!"function_entry_count", i64 1000}
+; CHECK: [[PROF_1]] = !{!"branch_weights", i32 2, i32 3}
+
diff --git a/llvm/test/Transforms/AggressiveInstCombine/trunc_select_cmp.ll b/llvm/test/Transforms/AggressiveInstCombine/trunc_select_cmp.ll
index ac9cf2dbd89b8..5252fd93e4d97 100644
--- a/llvm/test/Transforms/AggressiveInstCombine/trunc_select_cmp.ll
+++ b/llvm/test/Transforms/AggressiveInstCombine/trunc_select_cmp.ll
@@ -1,12 +1,13 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
 ; RUN: opt < %s -passes=aggressive-instcombine -S | FileCheck %s
 
-define dso_local i16 @cmp_select_sext_const(i8 %a) {
+define dso_local i16 @cmp_select_sext_const(i8 %a) !prof !0 {
 ; CHECK-LABEL: @cmp_select_sext_const(
+; CHECK: !prof [[PROF_0:![0-9]+]] {
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[CONV:%.*]] = sext i8 [[A:%.*]] to i32
 ; CHECK-NEXT:    [[CMP:%.*]] = icmp slt i32 [[CONV]], 109
-; CHECK-NEXT:    [[COND:%.*]] = select i1 [[CMP]], i32 109, i32 [[CONV]]
+; CHECK-NEXT:    [[COND:%.*]] = select i1 [[CMP]], i32 109, i32 [[CONV]], !prof [[PROF_1:![0-9]+]]
 ; CHECK-NEXT:    [[CONV4:%.*]] = trunc i32 [[COND]] to i16
 ; CHECK-NEXT:    ret i16 [[CONV4]]
 ;
@@ -209,3 +210,6 @@ define i16 @cmp_select_unsigned_const_i16Const_noTransformation(i8 %a) {
   ret i16 %conv4
 }
 
+!0 = !{!"function_entry_count", i64 1000}
+; CHECK: [[PROF_0]] = !{!"function_entry_count", i64 1000}
+; CHECK: [[PROF_1]] = !{!"branch_weights", i32 2, i32 3}

>From a88c0a2c2783dd77a0878e3c0b1fc6d7fd10712f Mon Sep 17 00:00:00 2001
From: Jin Huang <jingold at google.com>
Date: Thu, 9 Oct 2025 06:36:51 +0000
Subject: [PATCH 2/2] Fix the trunc select optimization to not produce prof
 metadata.

---
 llvm/lib/Transforms/AggressiveInstCombine/TruncInstCombine.cpp | 2 +-
 llvm/test/Transforms/AggressiveInstCombine/trunc_select.ll     | 3 ++-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/llvm/lib/Transforms/AggressiveInstCombine/TruncInstCombine.cpp b/llvm/lib/Transforms/AggressiveInstCombine/TruncInstCombine.cpp
index 38f3a81bc2c99..9150b58d0acf1 100644
--- a/llvm/lib/Transforms/AggressiveInstCombine/TruncInstCombine.cpp
+++ b/llvm/lib/Transforms/AggressiveInstCombine/TruncInstCombine.cpp
@@ -459,7 +459,7 @@ void TruncInstCombine::ReduceExpressionGraph(Type *SclTy) {
       Value *Op0 = I->getOperand(0);
       Value *LHS = getReducedOperand(I->getOperand(1), SclTy);
       Value *RHS = getReducedOperand(I->getOperand(2), SclTy);
-      Res = Builder.CreateSelect(Op0, LHS, RHS, "select", I);
+      Res = Builder.CreateSelect(Op0, LHS, RHS, "", I);
       break;
     }
     case Instruction::PHI: {
diff --git a/llvm/test/Transforms/AggressiveInstCombine/trunc_select.ll b/llvm/test/Transforms/AggressiveInstCombine/trunc_select.ll
index 12da17abcfdd4..93522119340e3 100644
--- a/llvm/test/Transforms/AggressiveInstCombine/trunc_select.ll
+++ b/llvm/test/Transforms/AggressiveInstCombine/trunc_select.ll
@@ -13,7 +13,7 @@ define dso_local i16 @select_i16(i16 %a, i16 %b, i1 %cond) !prof !0 {
 entry:
   %conv0 = sext i16 %a to i32
   %conv1 = sext i16 %b to i32
-  %sel = select i1 %cond, i32 %conv0, i32 %conv1
+  %sel = select i1 %cond, i32 %conv0, i32 %conv1, !prof !1
   %conv4 = trunc i32 %sel to i16
   ret i16 %conv4
 }
@@ -136,6 +136,7 @@ entry:
 }
 
 !0 = !{!"function_entry_count", i64 1000}
+!1 = !{!"branch_weights", i32 2, i32 3}
 ; CHECK: [[PROF_0]] = !{!"function_entry_count", i64 1000}
 ; CHECK: [[PROF_1]] = !{!"branch_weights", i32 2, i32 3}