[ARM] Fix unwind info for Thumb1 functions that save high registers.

There were two issues here: one, some of the relevant instructions were
missing the expected "FrameSetup" flag, and two,
ARMAsmPrinter::EmitUnwindingInstruction wasn't expecting "mov"
instructions in the prologue.

I'm sticking the additional state into ARMFunctionInfo so it's obvious
it only applies to the current function.

I considered a few alternative approaches where we would compute the
correct unwind information as part of the prologue/epilogue lowering,
but it seems like a lot of work to introduce pseudo-instructions, and
the current code seems to be reliable enough.

Fixes https://bugs.llvm.org/show_bug.cgi?id=42408.

Differential Revision: https://reviews.llvm.org/D63964

llvm-svn: 364970

1 files changed, 13 insertions, 5 deletions

diff --git a/llvm/lib/Target/ARM/ARMAsmPrinter.cpp b/llvm/lib/Target/ARM/ARMAsmPrinter.cpp
index d217cda4adc..e29077266fc 100644
--- a/llvm/lib/Target/ARM/ARMAsmPrinter.cpp
+++ b/llvm/lib/Target/ARM/ARMAsmPrinter.cpp
@@ -1071,7 +1071,6 @@ void ARMAsmPrinter::EmitUnwindingInstruction(const MachineInstr *MI) {
   const TargetRegisterInfo *TargetRegInfo =
     MF.getSubtarget().getRegisterInfo();
   const MachineRegisterInfo &MachineRegInfo = MF.getRegInfo();
-  const ARMFunctionInfo &AFI = *MF.getInfo<ARMFunctionInfo>();
 
   unsigned FramePtr = TargetRegInfo->getFrameRegister(MF);
   unsigned Opc = MI->getOpcode();
@@ -1135,7 +1134,12 @@ void ARMAsmPrinter::EmitUnwindingInstruction(const MachineInstr *MI) {
           Pad += Width;
           continue;
         }
-        RegList.push_back(MO.getReg());
+        // Check for registers that are remapped (for a Thumb1 prologue that
+        // saves high registers).
+        unsigned Reg = MO.getReg();
+        if (unsigned RemappedReg = AFI->EHPrologueRemappedRegs.lookup(Reg))
+          Reg = RemappedReg;
+        RegList.push_back(Reg);
       }
       break;
     case ARM::STR_PRE_IMM:
@@ -1185,7 +1189,7 @@ void ARMAsmPrinter::EmitUnwindingInstruction(const MachineInstr *MI) {
         unsigned CPI = MI->getOperand(1).getIndex();
         const MachineConstantPool *MCP = MF.getConstantPool();
         if (CPI >= MCP->getConstants().size())
-          CPI = AFI.getOriginalCPIdx(CPI);
+          CPI = AFI->getOriginalCPIdx(CPI);
         assert(CPI != -1U && "Invalid constpool index");
 
         // Derive the actual offset.
@@ -1215,8 +1219,12 @@ void ARMAsmPrinter::EmitUnwindingInstruction(const MachineInstr *MI) {
     } else if (DstReg == ARM::SP) {
       MI->print(errs());
       llvm_unreachable("Unsupported opcode for unwinding information");
-    }
-    else {
+    } else if (Opc == ARM::tMOVr) {
+      // If a Thumb1 function spills r8-r11, we copy the values to low
+      // registers before pushing them. Record the copy so we can emit the
+      // correct ".save" later.
+      AFI->EHPrologueRemappedRegs[DstReg] = SrcReg;
+    } else {
       MI->print(errs());
       llvm_unreachable("Unsupported opcode for unwinding information");
     }