[llvm-branch-commits] [llvm] CodeGen: Synthesize "float-abi" module flag from -float-abi (PR #215795)

[Matt Arsenault via llvm-branch-commits]

https://github.com/arsenm created https://github.com/llvm/llvm-project/pull/215795

Avoid annoying test updates when the corresponding TargetOptions
field is removed. Make the -float-abi llc/opt option a lit test
convenience that records the floating-point ABI in the IR,
mirroring how -mcpu/-mattr are recorded as function attributes.

Co-authored-by: Claude (Claude-Opus-4.8) <noreply at anthropic.com>

>From 05a4564d72120bae863530757157d6104d40e23e Mon Sep 17 00:00:00 2001
From: Matt Arsenault <Matthew.Arsenault at amd.com>
Date: Mon, 20 Jul 2026 19:28:58 +0200
Subject: [PATCH] CodeGen: Synthesize "float-abi" module flag from -float-abi

Avoid annoying test updates when the corresponding TargetOptions
field is removed. Make the -float-abi llc/opt option a lit test
convenience that records the floating-point ABI in the IR,
mirroring how -mcpu/-mattr are recorded as function attributes.

Co-authored-by: Claude (Claude-Opus-4.8) <noreply at anthropic.com>
---
 llvm/lib/CodeGen/CommandFlags.cpp             | 12 ++++++-
 .../CodeGen/ARM/float-abi-synthesize-flag.ll  | 32 +++++++++++++++++++
 2 files changed, 43 insertions(+), 1 deletion(-)
 create mode 100644 llvm/test/CodeGen/ARM/float-abi-synthesize-flag.ll

diff --git a/llvm/lib/CodeGen/CommandFlags.cpp b/llvm/lib/CodeGen/CommandFlags.cpp
index 306c0ff7c704b..88987d0bc5558 100644
--- a/llvm/lib/CodeGen/CommandFlags.cpp
+++ b/llvm/lib/CodeGen/CommandFlags.cpp
@@ -270,7 +270,9 @@ codegen::RegisterCodeGenFlags::RegisterCodeGenFlags() {
   CGBINDOPT(EnableHonorSignDependentRoundingFPMath);
 
   static cl::opt<FloatABI::ABIType> FloatABIForCalls(
-      "float-abi", cl::desc("Choose float ABI type"),
+      "float-abi",
+      cl::desc(
+          "Choose float ABI type (writes the \"float-abi\" IR module flag)"),
       cl::init(FloatABI::Default),
       cl::values(clEnumValN(FloatABI::Default, "default",
                             "Target default float ABI type"),
@@ -774,6 +776,14 @@ void codegen::setFunctionAttributes(Function &F, StringRef CPU,
 
 void codegen::setFunctionAttributes(Module &M, StringRef CPU,
                                     StringRef Features, StringRef TuneCPU) {
+  // Synthesize the "float-abi" module flag from the -float-abi option,
+  FloatABI::ABIType ABI = getFloatABIForCalls();
+  if (ABI != FloatABI::Default && !M.getModuleFlag("float-abi")) {
+    M.addModuleFlag(
+        Module::Error, "float-abi",
+        MDString::get(M.getContext(), FloatABI::getABITypeName(ABI)));
+  }
+
   for (Function &F : M)
     setFunctionAttributes(F, CPU, Features, TuneCPU);
 }
diff --git a/llvm/test/CodeGen/ARM/float-abi-synthesize-flag.ll b/llvm/test/CodeGen/ARM/float-abi-synthesize-flag.ll
new file mode 100644
index 0000000000000..ce4d47d18010f
--- /dev/null
+++ b/llvm/test/CodeGen/ARM/float-abi-synthesize-flag.ll
@@ -0,0 +1,32 @@
+; Check behavior of the -float-abi command-line option; it should
+; synthesize the "float-abi" module flag, unless one is already
+; present
+
+; RUN: split-file %s %t
+
+; -float-abi=hard writes the module flag.
+; RUN: llc -mtriple=armv7-none-eabi -float-abi=hard -stop-after=finalize-isel %t/none.ll -o - | FileCheck %s --check-prefix=HARD
+
+; -float-abi=soft writes the module flag.
+; RUN: llc -mtriple=armv7-none-eabi -float-abi=soft -stop-after=finalize-isel %t/none.ll -o - | FileCheck %s --check-prefix=SOFT
+
+; Without -float-abi, no flag is synthesized.
+; RUN: llc -mtriple=armv7-none-eabi -stop-after=finalize-isel %t/none.ll -o - | FileCheck %s --check-prefix=NONE
+
+; An explicit in-IR flag is not overridden by -float-abi.
+; RUN: llc -mtriple=armv7-none-eabi -float-abi=soft -stop-after=finalize-isel %t/hard.ll -o - | FileCheck %s --check-prefix=HARD
+
+;--- none.ll
+define void @f() {
+  ret void
+}
+; HARD: !{i32 1, !"float-abi", !"hard"}
+; SOFT: !{i32 1, !"float-abi", !"soft"}
+; NONE-NOT: !"float-abi"
+
+;--- hard.ll
+define void @f() {
+  ret void
+}
+!llvm.module.flags = !{!0}
+!0 = !{i32 1, !"float-abi", !"hard"}