[llvm] [FMV][GlobalOpt] Enable static resolution of non-FMV callers. (PR #124314)

[Alexandros Lamprineas via llvm-commits]

https://github.com/labrinea created https://github.com/llvm/llvm-project/pull/124314

The undetectable FMV features predres and ls64 have been removed, therefore the optimization is now re-enabled. The llvm testsuite Graviton4 bots are expected to remain green.

>From 632655bc3bc8fc794d70c039d564cf0a323ff0f9 Mon Sep 17 00:00:00 2001
From: Alexandros Lamprineas <alexandros.lamprineas at arm.com>
Date: Fri, 24 Jan 2025 17:27:01 +0000
Subject: [PATCH] [FMV][GlobalOpt] Enable static resolution of non-FMV callers.

The undetectable FMV features predres and ls64 have been removed,
therefore the optimization is now re-enabled. The llvm testsuite
Graviton4 bots are expected to remain green.
---
 llvm/lib/Transforms/IPO/GlobalOpt.cpp               | 11 +----------
 llvm/test/Transforms/GlobalOpt/resolve-fmv-ifunc.ll |  2 +-
 2 files changed, 2 insertions(+), 11 deletions(-)

diff --git a/llvm/lib/Transforms/IPO/GlobalOpt.cpp b/llvm/lib/Transforms/IPO/GlobalOpt.cpp
index 00c20ad5f37094..9586fc97a39f70 100644
--- a/llvm/lib/Transforms/IPO/GlobalOpt.cpp
+++ b/llvm/lib/Transforms/IPO/GlobalOpt.cpp
@@ -95,20 +95,11 @@ STATISTIC(NumIFuncsDeleted, "Number of IFuncs removed");
 STATISTIC(NumGlobalArraysPadded,
           "Number of global arrays padded to alignment boundary");
 
-// FIXME:
-// Optimizing non-FMV callers is causing a regression in the llvm test suite,
-// specifically a 'predres' version is unexpectedly trapping on GravitonG4.
-// My explanation is that when the caller in not a versioned function, the
-// compiler exclusively relies on the command line option, or target attribute
-// to deduce whether a feature is available. However, there is no guarantee
-// that in reality the host supports those implied features, which arguably
-// is a user error. This option allows disabling the optimization as a short
-// term workaround to keep the bots green.
 static cl::opt<bool>
     OptimizeNonFMVCallers("optimize-non-fmv-callers",
                           cl::desc("Statically resolve calls to versioned "
                                    "functions from non-versioned callers."),
-                          cl::init(false), cl::Hidden);
+                          cl::init(true), cl::Hidden);
 
 static cl::opt<bool>
     EnableColdCCStressTest("enable-coldcc-stress-test",
diff --git a/llvm/test/Transforms/GlobalOpt/resolve-fmv-ifunc.ll b/llvm/test/Transforms/GlobalOpt/resolve-fmv-ifunc.ll
index fa817a8cbf417f..4b6a19d3f05cf5 100644
--- a/llvm/test/Transforms/GlobalOpt/resolve-fmv-ifunc.ll
+++ b/llvm/test/Transforms/GlobalOpt/resolve-fmv-ifunc.ll
@@ -221,7 +221,7 @@ resolver_entry:
 define i32 @caller4() #8 {
 ; CHECK-LABEL: define i32 @caller4(
 ; CHECK-SAME: ) local_unnamed_addr #[[ATTR7:[0-9]+]] {
-; CHECK:    [[CALL:%.*]] = tail call i32 @test_non_fmv_caller()
+; CHECK:    [[CALL:%.*]] = tail call i32 @test_non_fmv_caller._Maes()
 ;
 entry:
   %call = tail call i32 @test_non_fmv_caller()