[llvm] [sroa][profcheck] Vector selects have "unknown" branch weights (PR #163319)

Tue Oct 14 10:27:42 PDT 2025

https://github.com/mtrofin updated https://github.com/llvm/llvm-project/pull/163319

>From 683812988a6844da2834e1defdafb1f5650edc50 Mon Sep 17 00:00:00 2001
From: Mircea Trofin <mtrofin at google.com>
Date: Mon, 13 Oct 2025 20:50:10 -0700
Subject: [PATCH] [sroa][profcheck] Vector selects have "unknown" branch
 weights

---
 llvm/lib/Transforms/Scalar/SROA.cpp      |  4 +++-
 llvm/test/Transforms/SROA/slice-width.ll | 19 ++++++++++++++++---
 llvm/utils/profcheck-xfail.txt           |  8 --------
 3 files changed, 19 insertions(+), 12 deletions(-)

diff --git a/llvm/lib/Transforms/Scalar/SROA.cpp b/llvm/lib/Transforms/Scalar/SROA.cpp
index d2f09e9f3c639..578fec772603f 100644
--- a/llvm/lib/Transforms/Scalar/SROA.cpp
+++ b/llvm/lib/Transforms/Scalar/SROA.cpp
@@ -2667,7 +2667,9 @@ static Value *insertVector(IRBuilderTy &IRB, Value *Old, Value *V,
   for (unsigned i = 0; i != cast<FixedVectorType>(VecTy)->getNumElements(); ++i)
     Mask2.push_back(IRB.getInt1(i >= BeginIndex && i < EndIndex));
 
-  V = IRB.CreateSelect(ConstantVector::get(Mask2), V, Old, Name + "blend");
+  // No profiling support for vector selects.
+  V = IRB.CreateSelectWithUnknownProfile(ConstantVector::get(Mask2), V, Old,
+                                         DEBUG_TYPE, Name + "blend");
 
   LLVM_DEBUG(dbgs() << "    blend: " << *V << "\n");
   return V;
diff --git a/llvm/test/Transforms/SROA/slice-width.ll b/llvm/test/Transforms/SROA/slice-width.ll
index eabb6978c9125..3b77e49e78358 100644
--- a/llvm/test/Transforms/SROA/slice-width.ll
+++ b/llvm/test/Transforms/SROA/slice-width.ll
@@ -1,4 +1,4 @@
-; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --check-globals
 ; RUN: opt < %s -passes='sroa<preserve-cfg>' -S | FileCheck %s --check-prefixes=CHECK,CHECK-PRESERVE-CFG
 ; RUN: opt < %s -passes='sroa<modify-cfg>' -S | FileCheck %s --check-prefixes=CHECK,CHECK-MODIFY-CFG
 target datalayout = "e-p:64:64:64-p1:16:16:16-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:64:64-f80:128-v64:64:64-v128:128:128-a0:0:64-n8:16:32:64"
@@ -8,6 +8,10 @@ declare void @llvm.memset.p0.i32(ptr nocapture, i8, i32, i1) nounwind
 declare void @llvm.memset.p0.i64(ptr nocapture, i8, i64, i1) nounwind
 
 ; This tests that allocas are not split into slices that are not byte width multiple
+;.
+; CHECK: @foo_copy_source = external constant %union.Foo
+; CHECK: @i64_sink = global i64 0
+;.
 define void @no_split_on_non_byte_width(i32) {
 ; CHECK-LABEL: @no_split_on_non_byte_width(
 ; CHECK-NEXT:    [[ARG_SROA_0:%.*]] = alloca i8, align 8
@@ -92,12 +96,12 @@ declare i32 @memcpy_vec3float_helper(ptr)
 
 ; PR18726: Check that SROA does not rewrite a 12-byte memcpy into a 16-byte
 ; vector store, hence accidentally putting gibberish onto the stack.
-define i32 @memcpy_vec3float_widening(ptr %x) {
+define i32 @memcpy_vec3float_widening(ptr %x) !prof !0 {
 ; CHECK-LABEL: @memcpy_vec3float_widening(
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[TMP1_SROA_0_0_COPYLOAD:%.*]] = load <3 x float>, ptr [[X:%.*]], align 4
 ; CHECK-NEXT:    [[TMP1_SROA_0_0_VEC_EXPAND:%.*]] = shufflevector <3 x float> [[TMP1_SROA_0_0_COPYLOAD]], <3 x float> poison, <4 x i32> <i32 0, i32 1, i32 2, i32 poison>
-; CHECK-NEXT:    [[TMP1_SROA_0_0_VECBLEND:%.*]] = select <4 x i1> <i1 true, i1 true, i1 true, i1 false>, <4 x float> [[TMP1_SROA_0_0_VEC_EXPAND]], <4 x float> undef
+; CHECK-NEXT:    [[TMP1_SROA_0_0_VECBLEND:%.*]] = select <4 x i1> <i1 true, i1 true, i1 true, i1 false>, <4 x float> [[TMP1_SROA_0_0_VEC_EXPAND]], <4 x float> undef, !prof [[PROF1:![0-9]+]]
 ; CHECK-NEXT:    [[TMP2:%.*]] = alloca [[S_VEC3FLOAT:%.*]], align 4
 ; CHECK-NEXT:    [[TMP1_SROA_0_0_VEC_EXTRACT:%.*]] = shufflevector <4 x float> [[TMP1_SROA_0_0_VECBLEND]], <4 x float> poison, <3 x i32> <i32 0, i32 1, i32 2>
 ; CHECK-NEXT:    store <3 x float> [[TMP1_SROA_0_0_VEC_EXTRACT]], ptr [[TMP2]], align 4
@@ -158,6 +162,15 @@ define i1 @presplit_overlarge_load() {
   %L2 = load i1, ptr %A
   ret i1 %L2
 }
+!0 = !{!"function_entry_count", i32 10}
+
+;.
+; CHECK: attributes #[[ATTR0:[0-9]+]] = { nocallback nofree nounwind willreturn memory(argmem: readwrite) }
+; CHECK: attributes #[[ATTR1:[0-9]+]] = { nocallback nofree nounwind willreturn memory(argmem: write) }
+;.
+; CHECK: [[META0:![0-9]+]] = !{!"function_entry_count", i32 10}
+; CHECK: [[PROF1]] = !{!"unknown", !"sroa"}
+;.
 ;; NOTE: These prefixes are unused and the list is autogenerated. Do not add tests below this line:
 ; CHECK-MODIFY-CFG: {{.*}}
 ; CHECK-PRESERVE-CFG: {{.*}}
diff --git a/llvm/utils/profcheck-xfail.txt b/llvm/utils/profcheck-xfail.txt
index a5c5426870a7d..3f8be5e240762 100644
--- a/llvm/utils/profcheck-xfail.txt
+++ b/llvm/utils/profcheck-xfail.txt
@@ -1310,14 +1310,6 @@ Transforms/SimpleLoopUnswitch/pr60736.ll
 Transforms/SimpleLoopUnswitch/trivial-unswitch-freeze-individual-conditions.ll
 Transforms/SimpleLoopUnswitch/trivial-unswitch.ll
 Transforms/SimpleLoopUnswitch/trivial-unswitch-logical-and-or.ll
-Transforms/SROA/phi-gep.ll
-Transforms/SROA/scalable-vectors-with-known-vscale.ll
-Transforms/SROA/select-gep.ll
-Transforms/SROA/select-load.ll
-Transforms/SROA/slice-width.ll
-Transforms/SROA/vector-conversion.ll
-Transforms/SROA/vector-promotion-cannot-tree-structure-merge.ll
-Transforms/SROA/vector-promotion.ll
 Transforms/StackProtector/cross-dso-cfi-stack-chk-fail.ll
 Transforms/StructurizeCFG/AMDGPU/uniform-regions.ll
 Transforms/StructurizeCFG/hoist-zerocost.ll

