[PATCH] D112073: [PowerPC] Emit warning when SP is clobbered by asm

[Quinn Pham via Phabricator via llvm-commits]

quinnp created this revision.
Herald added subscribers: shchenz, kbarton, hiraditya, nemanjai.
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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.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D112073

Files:
  llvm/lib/Target/PowerPC/PPCRegisterInfo.cpp
  llvm/lib/Target/PowerPC/PPCRegisterInfo.h
  llvm/test/CodeGen/PowerPC/inline-asm-clobber-warning.ll


Index: llvm/test/CodeGen/PowerPC/inline-asm-clobber-warning.ll
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/PowerPC/inline-asm-clobber-warning.ll
@@ -0,0 +1,10 @@
+; RUN: llc < %s -verify-machineinstrs -mtriple=powerpc-unknown-unkown \
+; RUN:   -mcpu=pwr7 2>&1 | FileCheck %s
+
+; CHECK: warning: inline asm clobber list contains reserved registers: R1
+; CHECK-NEXT: note: Reserved registers on the clobber list may not be preserved across the asm statement, and clobbering them may lead to undefined behaviour.
+define void @test_r1_clobber() {
+entry:
+  call void asm sideeffect "nop", "~{r1}"()
+  ret void
+}
Index: llvm/lib/Target/PowerPC/PPCRegisterInfo.h
===================================================================
--- llvm/lib/Target/PowerPC/PPCRegisterInfo.h
+++ llvm/lib/Target/PowerPC/PPCRegisterInfo.h
@@ -91,6 +91,8 @@
   void adjustStackMapLiveOutMask(uint32_t *Mask) const override;
 
   BitVector getReservedRegs(const MachineFunction &MF) const override;
+  bool isAsmClobberable(const MachineFunction &MF,
+                        MCRegister PhysReg) const override;
   bool isCallerPreservedPhysReg(MCRegister PhysReg,
                                 const MachineFunction &MF) const override;
 
Index: llvm/lib/Target/PowerPC/PPCRegisterInfo.cpp
===================================================================
--- llvm/lib/Target/PowerPC/PPCRegisterInfo.cpp
+++ llvm/lib/Target/PowerPC/PPCRegisterInfo.cpp
@@ -390,6 +390,12 @@
   return Reserved;
 }
 
+bool PPCRegisterInfo::isAsmClobberable(const MachineFunction &MF,
+                                       MCRegister PhysReg) const {
+  // The stack pointer (R1) is not clobberable by inline asm
+  return PhysReg != PPC::R1;
+}
+
 bool PPCRegisterInfo::requiresFrameIndexScavenging(const MachineFunction &MF) const {
   const PPCSubtarget &Subtarget = MF.getSubtarget<PPCSubtarget>();
   const PPCInstrInfo *InstrInfo =  Subtarget.getInstrInfo();


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