[clang] [clang] Unify -mspeculative-load-hardening as a benign compiler option (PR #166640)

[Cyndy Ishida via cfe-commits]

https://github.com/cyndyishida created https://github.com/llvm/llvm-project/pull/166640

Before this patch, compilations using modules &
`-mspeculative-load-hardening` failed because it was not consistent whether this option impacts module compatibility.

This repairs it by always treating it as benign. This was determined by checking if the option enables any kind of preprocessor checks and comparing how the compiler handles a similar option that impacts codegen (-fvisibility=hidden) but is more widely used.

resolves: rdar://163985667

>From 7b269b6e75253a03adb72b736d53cc5555f0291f Mon Sep 17 00:00:00 2001
From: Cyndy Ishida <cyndy_ishida at apple.com>
Date: Wed, 5 Nov 2025 12:46:40 -0800
Subject: [PATCH] [clang] Unify -mspeculative-load-hardening as a benign
 compiler option

Before this patch, compilations using modules &
-mspeculative-load-hardening because of a configuration mismatch because
it was not consistent whether this option impacts module compatibility.

This repairs it by always treating it as benign. This was determined by
checking if the option enables any kind of preprocessor checks and
comparing how the compiler handles a similiar option that impacts codegen
(-fvisibility=hidden) but is more widely used.
---
 clang/include/clang/Basic/LangOptions.def     | 2 +-
 clang/test/ClangScanDeps/strip-codegen-args.m | 6 ++++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/clang/include/clang/Basic/LangOptions.def b/clang/include/clang/Basic/LangOptions.def
index d3cca82b4bdff..40fc66ea12e34 100644
--- a/clang/include/clang/Basic/LangOptions.def
+++ b/clang/include/clang/Basic/LangOptions.def
@@ -454,7 +454,7 @@ LANGOPT(BranchTargetEnforcement, 1, 0, NotCompatible, "Branch-target enforcement
 LANGOPT(BranchProtectionPAuthLR, 1, 0, NotCompatible, "Use PC as a diversifier using PAuthLR NOP instructions.")
 LANGOPT(GuardedControlStack, 1, 0, NotCompatible, "Guarded control stack enabled")
 
-LANGOPT(SpeculativeLoadHardening, 1, 0, NotCompatible, "Speculative load hardening enabled")
+LANGOPT(SpeculativeLoadHardening, 1, 0, Benign, "Speculative load hardening enabled")
 
 LANGOPT(RelativeCXXABIVTables, 1, 0, NotCompatible,
         "Use an ABI-incompatible v-table layout that uses relative references")
diff --git a/clang/test/ClangScanDeps/strip-codegen-args.m b/clang/test/ClangScanDeps/strip-codegen-args.m
index 71171f4983386..f2cec6281f7df 100644
--- a/clang/test/ClangScanDeps/strip-codegen-args.m
+++ b/clang/test/ClangScanDeps/strip-codegen-args.m
@@ -16,6 +16,7 @@
 // CHECK-NOT:          "-flto"
 // CHECK-NOT:          "-fno-autolink"
 // CHECK-NOT:          "-mrelax-relocations=no"
+// CHECK-NOT:          "-mspeculative-load-hardening"
 // CHECK:            ]
 // CHECK:            "name": "A"
 // CHECK:          }
@@ -39,6 +40,11 @@
     "command": "clang -Imodules/A -fmodules -fmodules-cache-path=DIR/module-cache -fimplicit-modules -O2 -flto=full -fsyntax-only DIR/t3.m",
     "file": "DIR/t2.m"
   }
+  {
+    "directory": "DIR",
+    "command": "clang -Imodules/A -fmodules -fmodules-cache-path=DIR/module-cache -fimplicit-modules -O2 -mspeculative-load-hardening -fsyntax-only DIR/t3.m",
+    "file": "DIR/t3.m"
+  }
 ]
 
 //--- modules/A/module.modulemap