[AArch64] Mark function calls as possibly changing FPCR

This patch does the same changes as D111433 for PowerPC and D139549 for
X86, - in the strictfp function all calls are marked as implicit defs of
FPCR. It prevents from moving FP operations across function calls, which
may change rounding mode, as fesetround does.

Differential Revision: https://reviews.llvm.org/D143001

llvm/lib/Target/AArch64/AArch64ISelLowering.cpp

@@ -14946,6 +14946,11 @@ AArch64TargetLowering::getScratchRegisters(CallingConv::ID) const {
   return ScratchRegs;
 }
 
+const MCPhysReg *AArch64TargetLowering::getRoundingControlRegisters() const {
+  static const MCPhysReg RCRegs[] = {AArch64::FPCR, 0};
+  return RCRegs;
+}
+
 bool
 AArch64TargetLowering::isDesirableToCommuteWithShift(const SDNode *N,
                                                      CombineLevel Level) const {

llvm/lib/Target/AArch64/AArch64ISelLowering.h

@@ -670,6 +670,7 @@ class AArch64TargetLowering : public TargetLowering {
                                      CodeGenOpt::Level OptLevel) const override;
 
   const MCPhysReg *getScratchRegisters(CallingConv::ID CC) const override;
+  const MCPhysReg *getRoundingControlRegisters() const override;
 
   /// Returns false if N is a bit extraction pattern of (X >> C) & Mask.
   bool isDesirableToCommuteWithShift(const SDNode *N,

llvm/test/CodeGen/AArch64/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)