[PowerPC] Emit warning when SP is clobbered by asm

This patch emits a warning when the stack pointer register (`R1`) is found in
the clobber list of an inline asm statement. Clobbering the stack pointer is
not supported.

Reviewed By: #powerpc, nemanjai

Differential Revision: https://reviews.llvm.org/D112073

1 files changed, 12 insertions, 0 deletions

diff --git a/llvm/lib/Target/PowerPC/PPCRegisterInfo.cpp b/llvm/lib/Target/PowerPC/PPCRegisterInfo.cpp
index 422b3db..76b016c0 100644
--- a/llvm/lib/Target/PowerPC/PPCRegisterInfo.cpp
+++ b/llvm/lib/Target/PowerPC/PPCRegisterInfo.cpp
@@ -390,6 +390,18 @@ BitVector PPCRegisterInfo::getReservedRegs(const MachineFunction &MF) const {
   return Reserved;
 }
 
+bool PPCRegisterInfo::isAsmClobberable(const MachineFunction &MF,
+                                       MCRegister PhysReg) const {
+  // We cannot use getReservedRegs() to find the registers that are not asm
+  // clobberable because there are some reserved registers which can be
+  // clobbered by inline asm. For example, when LR is clobbered, the register is
+  // saved and restored. We will hardcode the registers that are not asm
+  // cloberable in this function.
+
+  // The stack pointer (R1/X1) is not clobberable by inline asm
+  return PhysReg != PPC::R1 && PhysReg != PPC::X1;
+}
+
 bool PPCRegisterInfo::requiresFrameIndexScavenging(const MachineFunction &MF) const {
   const PPCSubtarget &Subtarget = MF.getSubtarget<PPCSubtarget>();
   const PPCInstrInfo *InstrInfo =  Subtarget.getInstrInfo();