[llvm] [InstCombine] Propagate Profile when Folding Implied Conditionals (PR #163412)

[Aiden Grossman via llvm-commits]

https://github.com/boomanaiden154 created https://github.com/llvm/llvm-project/pull/163412

In the case where we have a conditional that is implied by a previous conditional (like x < 10 => x < 20 in a select), we can simply propagate the profile information along the select.

>From 0ac50a3ba6f48bc9729d026bba0a919ceec5aac4 Mon Sep 17 00:00:00 2001
From: Aiden Grossman <aidengrossman at google.com>
Date: Tue, 14 Oct 2025 15:25:51 +0000
Subject: [PATCH] [InstCombine] Propagate Profile when Folding Implied
 Conditionals

In the case where we have a conditional that is implied by a previous
conditional (like x < 10 => x < 20 in a select), we can simply propagate
the profile information along the select.
---
 .../Transforms/InstCombine/InstCombineSelect.cpp  |  9 +++++++--
 .../select-safe-impliedcond-transforms.ll         | 15 +++++++++++----
 llvm/utils/profcheck-xfail.txt                    |  2 --
 3 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
index 6b67b48a138be..1f98bb3b29bad 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
@@ -2979,10 +2979,15 @@ Instruction *InstCombinerImpl::foldAndOrOfSelectUsingImpliedCond(Value *Op,
          "Op must be either i1 or vector of i1.");
   if (SI.getCondition()->getType() != Op->getType())
     return nullptr;
-  if (Value *V = simplifyNestedSelectsUsingImpliedCond(SI, Op, IsAnd, DL))
+  if (Value *V = simplifyNestedSelectsUsingImpliedCond(SI, Op, IsAnd, DL)) {
+    Instruction *MDFrom = nullptr;
+    if (!ProfcheckDisableMetadataFixes)
+      MDFrom = &SI;
     return SelectInst::Create(Op,
                               IsAnd ? V : ConstantInt::getTrue(Op->getType()),
-                              IsAnd ? ConstantInt::getFalse(Op->getType()) : V);
+                              IsAnd ? ConstantInt::getFalse(Op->getType()) : V,
+                              "", nullptr, MDFrom);
+  }
   return nullptr;
 }
 
diff --git a/llvm/test/Transforms/InstCombine/select-safe-impliedcond-transforms.ll b/llvm/test/Transforms/InstCombine/select-safe-impliedcond-transforms.ll
index ba34930dc14c1..bc988a9bbab04 100644
--- a/llvm/test/Transforms/InstCombine/select-safe-impliedcond-transforms.ll
+++ b/llvm/test/Transforms/InstCombine/select-safe-impliedcond-transforms.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=instcombine -S | FileCheck %s
 
 define i1 @a_true_implies_b_true(i8 %z, i1 %X, i1 %Y) {
@@ -34,15 +34,15 @@ define <2 x i1> @a_true_implies_b_true_vec(i8 %z0, <2 x i1> %X, <2 x i1> %Y) {
   ret <2 x i1> %res
 }
 
-define i1 @a_true_implies_b_true2(i8 %z, i1 %X, i1 %Y) {
+define i1 @a_true_implies_b_true2(i8 %z, i1 %X, i1 %Y) !prof !0 {
 ; CHECK-LABEL: @a_true_implies_b_true2(
 ; CHECK-NEXT:    [[A:%.*]] = icmp ugt i8 [[Z:%.*]], 20
-; CHECK-NEXT:    [[RES:%.*]] = select i1 [[A]], i1 [[X:%.*]], i1 false
+; CHECK-NEXT:    [[RES:%.*]] = select i1 [[A]], i1 [[X:%.*]], i1 false, !prof [[PROF1:![0-9]+]]
 ; CHECK-NEXT:    ret i1 [[RES]]
 ;
   %a = icmp ugt i8 %z, 20
   %b = icmp ugt i8 %z, 10
-  %sel = select i1 %b, i1 %X, i1 %Y
+  %sel = select i1 %b, i1 %X, i1 %Y, !prof !1
   %res = and i1 %a, %sel
   ret i1 %res
 }
@@ -258,3 +258,10 @@ define i1 @neg_icmp_eq_implies_trunc(i8 %x, i1 %c) {
   %sel2 = select i1 %cmp, i1 true, i1 %sel1
   ret i1 %sel2
 }
+
+!0 = !{!"function_entry_count", i64 1000}
+!1 = !{!"branch_weights", i32 2, i32 3}
+;.
+; CHECK: [[META0:![0-9]+]] = !{!"function_entry_count", i64 1000}
+; CHECK: [[PROF1]] = !{!"branch_weights", i32 2, i32 3}
+;.
diff --git a/llvm/utils/profcheck-xfail.txt b/llvm/utils/profcheck-xfail.txt
index 343c2bb7146c3..14c10c9654039 100644
--- a/llvm/utils/profcheck-xfail.txt
+++ b/llvm/utils/profcheck-xfail.txt
@@ -906,7 +906,6 @@ Transforms/InstCombine/select_frexp.ll
 Transforms/InstCombine/select.ll
 Transforms/InstCombine/select-min-max.ll
 Transforms/InstCombine/select-of-symmetric-selects.ll
-Transforms/InstCombine/select-safe-impliedcond-transforms.ll
 Transforms/InstCombine/select-safe-transforms.ll
 Transforms/InstCombine/select-select.ll
 Transforms/InstCombine/select-with-extreme-eq-cond.ll
@@ -1237,7 +1236,6 @@ Transforms/PartiallyInlineLibCalls/X86/good-prototype.ll
 Transforms/PGOProfile/chr-dead-pred.ll
 Transforms/PGOProfile/chr-dup-threshold.ll
 Transforms/PGOProfile/chr-lifetimes.ll
-Transforms/PGOProfile/chr.ll
 Transforms/PGOProfile/chr-poison.ll
 Transforms/PGOProfile/comdat.ll
 Transforms/PGOProfile/memop_profile_funclet_wasm.ll