[llvm] [ARM] Recognize abi tag module flags (PR #161306)

[via llvm-commits]

https://github.com/paperchalice updated https://github.com/llvm/llvm-project/pull/161306

>From 1e9297340c796134737044470363cd128dbe2789 Mon Sep 17 00:00:00 2001
From: PaperChalice <liujunchang97 at outlook.com>
Date: Mon, 29 Sep 2025 12:32:42 +0800
Subject: [PATCH] [ARM] Recognize some module flags

---
 llvm/lib/Target/ARM/ARMAsmPrinter.cpp         | 28 +++++++++++++++----
 .../CodeGen/ARM/build-attributes-module.ll    | 14 ++++++++++
 2 files changed, 36 insertions(+), 6 deletions(-)
 create mode 100644 llvm/test/CodeGen/ARM/build-attributes-module.ll

diff --git a/llvm/lib/Target/ARM/ARMAsmPrinter.cpp b/llvm/lib/Target/ARM/ARMAsmPrinter.cpp
index 1f773e2a7e0fc..125c002682012 100644
--- a/llvm/lib/Target/ARM/ARMAsmPrinter.cpp
+++ b/llvm/lib/Target/ARM/ARMAsmPrinter.cpp
@@ -701,9 +701,21 @@ void ARMAsmPrinter::emitAttributes() {
                       ARMBuildAttrs::AddressDirect);
   }
 
+  Metadata *MDEx = nullptr;
+  Metadata *MDDM = nullptr;
+  Metadata *MDNM = nullptr;
+  if (const Module *M = MMI->getModule()) {
+    MDEx = M->getModuleFlag("arm-eabi-fp-exceptions");
+    MDDM = M->getModuleFlag("arm-eabi-fp-denormal");
+    MDNM = M->getModuleFlag("arm-eabi-fp-number-model");
+  }
+
   // Set FP Denormals.
-  if (checkDenormalAttributeConsistency(*MMI->getModule(), "denormal-fp-math",
-                                        DenormalMode::getPreserveSign()))
+  if (auto *DM = mdconst::extract_or_null<ConstantInt>(MDDM))
+    ATS.emitAttribute(ARMBuildAttrs::ABI_FP_denormal, DM->getZExtValue());
+  else if (checkDenormalAttributeConsistency(*MMI->getModule(),
+                                             "denormal-fp-math",
+                                             DenormalMode::getPreserveSign()))
     ATS.emitAttribute(ARMBuildAttrs::ABI_FP_denormal,
                       ARMBuildAttrs::PreserveFPSign);
   else if (checkDenormalAttributeConsistency(*MMI->getModule(),
@@ -743,9 +755,11 @@ void ARMAsmPrinter::emitAttributes() {
   }
 
   // Set FP exceptions and rounding
-  if (checkFunctionsAttributeConsistency(*MMI->getModule(),
-                                         "no-trapping-math", "true") ||
-      TM.Options.NoTrappingFPMath)
+  if (auto *Ex = mdconst::extract_or_null<ConstantInt>(MDEx))
+    ATS.emitAttribute(ARMBuildAttrs::ABI_FP_exceptions, Ex->getZExtValue());
+  else if (checkFunctionsAttributeConsistency(*MMI->getModule(),
+                                              "no-trapping-math", "true") ||
+           TM.Options.NoTrappingFPMath)
     ATS.emitAttribute(ARMBuildAttrs::ABI_FP_exceptions,
                       ARMBuildAttrs::Not_Allowed);
   else {
@@ -759,7 +773,9 @@ void ARMAsmPrinter::emitAttributes() {
 
   // TM.Options.NoInfsFPMath && TM.Options.NoNaNsFPMath is the
   // equivalent of GCC's -ffinite-math-only flag.
-  if (TM.Options.NoInfsFPMath && TM.Options.NoNaNsFPMath)
+  if (auto *NM = mdconst::extract_or_null<ConstantInt>(MDNM))
+    ATS.emitAttribute(ARMBuildAttrs::ABI_FP_number_model, NM->getZExtValue());
+  else if (TM.Options.NoInfsFPMath && TM.Options.NoNaNsFPMath)
     ATS.emitAttribute(ARMBuildAttrs::ABI_FP_number_model,
                       ARMBuildAttrs::Allowed);
   else
diff --git a/llvm/test/CodeGen/ARM/build-attributes-module.ll b/llvm/test/CodeGen/ARM/build-attributes-module.ll
new file mode 100644
index 0000000000000..d7ac8e7df376f
--- /dev/null
+++ b/llvm/test/CodeGen/ARM/build-attributes-module.ll
@@ -0,0 +1,14 @@
+; RUN: llc %s -mtriple=arm-none-none-eabi -o - | FileCheck %s
+
+define void @f() {
+    ret void
+}
+
+!llvm.module.flags = !{!0, !1, !2}
+
+; CHECK: .eabi_attribute 20, 0
+!0 = !{i32 2, !"arm-eabi-fp-denormal", i32 0}
+; CHECK: .eabi_attribute 21, 1
+!1 = !{i32 2, !"arm-eabi-fp-exceptions", i32 1}
+; CHECK: .eabi_attribute 23, 1
+!2 = !{i32 2, !"arm-eabi-fp-number-model", i32 1}