[llvm] [ARM] Mark function calls as possibly changing FPSCR (PR #160699)

[Erik Enikeev via llvm-commits]

https://github.com/Varnike updated https://github.com/llvm/llvm-project/pull/160699

>From f26ecdaed31373ff233b03cbdf3a5da2ae1ecfe7 Mon Sep 17 00:00:00 2001
From: Erik Enikeev <evonatarius at gmail.com>
Date: Wed, 27 Aug 2025 18:10:26 +0300
Subject: [PATCH 1/2] [ARM] Mark function calls as possibly changing FPSCR

This patch does the same changes as D143001 for AArch64
---
 llvm/lib/Target/ARM/ARMISelLowering.cpp |  5 +++++
 llvm/lib/Target/ARM/ARMISelLowering.h   |  2 ++
 llvm/test/CodeGen/ARM/strict-fp-func.ll | 13 +++++++++++++
 3 files changed, 20 insertions(+)
 create mode 100644 llvm/test/CodeGen/ARM/strict-fp-func.ll

diff --git a/llvm/lib/Target/ARM/ARMISelLowering.cpp b/llvm/lib/Target/ARM/ARMISelLowering.cpp
index 2a40fb9b476f8..f13d5fe6f1c47 100644
--- a/llvm/lib/Target/ARM/ARMISelLowering.cpp
+++ b/llvm/lib/Target/ARM/ARMISelLowering.cpp
@@ -22004,6 +22004,11 @@ bool ARMTargetLowering::isComplexDeinterleavingOperationSupported(
           ScalarTy->isIntegerTy(32));
 }
 
+ArrayRef<MCPhysReg> ARMTargetLowering::getRoundingControlRegisters() const {
+  static const MCPhysReg RCRegs[] = {ARM::FPSCR};
+  return RCRegs;
+}
+
 Value *ARMTargetLowering::createComplexDeinterleavingIR(
     IRBuilderBase &B, ComplexDeinterleavingOperation OperationType,
     ComplexDeinterleavingRotation Rotation, Value *InputA, Value *InputB,
diff --git a/llvm/lib/Target/ARM/ARMISelLowering.h b/llvm/lib/Target/ARM/ARMISelLowering.h
index 26ff54cfe0b90..4942f81c694df 100644
--- a/llvm/lib/Target/ARM/ARMISelLowering.h
+++ b/llvm/lib/Target/ARM/ARMISelLowering.h
@@ -1005,6 +1005,8 @@ class VectorType;
 
     bool isUnsupportedFloatingType(EVT VT) const;
 
+    ArrayRef<MCPhysReg> getRoundingControlRegisters() const override;
+
     SDValue getCMOV(const SDLoc &dl, EVT VT, SDValue FalseVal, SDValue TrueVal,
                     SDValue ARMcc, SDValue Flags, SelectionDAG &DAG) const;
     SDValue getARMCmp(SDValue LHS, SDValue RHS, ISD::CondCode CC,
diff --git a/llvm/test/CodeGen/ARM/strict-fp-func.ll b/llvm/test/CodeGen/ARM/strict-fp-func.ll
new file mode 100644
index 0000000000000..198d4fdea6831
--- /dev/null
+++ b/llvm/test/CodeGen/ARM/strict-fp-func.ll
@@ -0,0 +1,13 @@
+; RUN: llc -mtriple aarch64-none-linux-gnu -stop-after=finalize-isel %s -o - | FileCheck %s
+
+define float @func_02(float %x, float %y) strictfp nounwind {
+  %call = call float @func_01(float %x) strictfp
+  %res = call float @llvm.experimental.constrained.fadd.f32(float %call, float %y, metadata !"round.dynamic", metadata !"fpexcept.ignore") strictfp
+  ret float %res
+}
+; CHECK-LABEL: name: func_02
+; CHECK:       BL @func_01, {{.*}}, implicit-def $fpcr
+
+
+declare float @func_01(float)
+declare float @llvm.experimental.constrained.fadd.f32(float, float, metadata, metadata)

>From 107563af1a46801d33226491c2c086984c161277 Mon Sep 17 00:00:00 2001
From: Erik Enikeev <evonatarius at gmail.com>
Date: Mon, 29 Sep 2025 15:42:33 +0300
Subject: [PATCH 2/2] fixup: use FPSCR_RM instead of FPSCR and correct test
 target

---
 llvm/lib/Target/ARM/ARMISelLowering.cpp | 2 +-
 llvm/test/CodeGen/ARM/strict-fp-func.ll | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/llvm/lib/Target/ARM/ARMISelLowering.cpp b/llvm/lib/Target/ARM/ARMISelLowering.cpp
index f13d5fe6f1c47..e70f337dd54dd 100644
--- a/llvm/lib/Target/ARM/ARMISelLowering.cpp
+++ b/llvm/lib/Target/ARM/ARMISelLowering.cpp
@@ -22005,7 +22005,7 @@ bool ARMTargetLowering::isComplexDeinterleavingOperationSupported(
 }
 
 ArrayRef<MCPhysReg> ARMTargetLowering::getRoundingControlRegisters() const {
-  static const MCPhysReg RCRegs[] = {ARM::FPSCR};
+  static const MCPhysReg RCRegs[] = {ARM::FPSCR_RM};
   return RCRegs;
 }
 
diff --git a/llvm/test/CodeGen/ARM/strict-fp-func.ll b/llvm/test/CodeGen/ARM/strict-fp-func.ll
index 198d4fdea6831..39bb2b46bdac5 100644
--- a/llvm/test/CodeGen/ARM/strict-fp-func.ll
+++ b/llvm/test/CodeGen/ARM/strict-fp-func.ll
@@ -1,4 +1,4 @@
-; RUN: llc -mtriple aarch64-none-linux-gnu -stop-after=finalize-isel %s -o - | FileCheck %s
+; RUN: llc -mtriple arm-none-eabi -stop-after=finalize-isel %s -o - | FileCheck %s
 
 define float @func_02(float %x, float %y) strictfp nounwind {
   %call = call float @func_01(float %x) strictfp
@@ -6,7 +6,7 @@ define float @func_02(float %x, float %y) strictfp nounwind {
   ret float %res
 }
 ; CHECK-LABEL: name: func_02
-; CHECK:       BL @func_01, {{.*}}, implicit-def $fpcr
+; CHECK:       BL @func_01, {{.*}}, implicit-def $fpscr_rm
 
 
 declare float @func_01(float)