The saved registers weren't being processed in the correct order. This lead to

the compact unwind claiming that one register was saved before another, which
isn't all that great in general. Process them in the natural order. Reverse the
list only when necessary for the algorithm.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@146612 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/X86/X86FrameLowering.cpp b/lib/Target/X86/X86FrameLowering.cpp
index 036043637fd0c291715510f1f1243a35ae4feeed..6a40cc1797419b2a132a4bfb6661c295035ca400 100644 (file)
--- a/lib/Target/X86/X86FrameLowering.cpp
+++ b/lib/Target/X86/X86FrameLowering.cpp
@@ -351,8 +351,7 @@ void X86FrameLowering::emitCalleeSavedFrameMoves(MachineFunction &MF,
 /// register. The number corresponds to the enum lists in
 /// compact_unwind_encoding.h.
 static int getCompactUnwindRegNum(const unsigned *CURegs, unsigned Reg) {
-  int Idx = 1;
-  for (; *CURegs; ++CURegs, ++Idx)
+  for (int Idx = 1; *CURegs; ++CURegs, ++Idx)
     if (*CURegs == Reg)
       return Idx;
 
@@ -388,12 +387,17 @@ encodeCompactUnwindRegistersWithoutFrame(unsigned SavedRegs[CU_NUM_SAVED_REGS],
   };
   const unsigned *CURegs = (Is64Bit ? CU64BitRegs : CU32BitRegs);
 
-  for (unsigned i = CU_NUM_SAVED_REGS - RegCount; i < CU_NUM_SAVED_REGS; ++i) {
+  for (unsigned i = 0; i != CU_NUM_SAVED_REGS; ++i) {
     int CUReg = getCompactUnwindRegNum(CURegs, SavedRegs[i]);
     if (CUReg == -1) return ~0U;
     SavedRegs[i] = CUReg;
   }
 
+  // Reverse the list.
+  std::swap(SavedRegs[0], SavedRegs[5]);
+  std::swap(SavedRegs[1], SavedRegs[4]);
+  std::swap(SavedRegs[2], SavedRegs[3]);
+
   uint32_t RenumRegs[CU_NUM_SAVED_REGS];
   for (unsigned i = CU_NUM_SAVED_REGS - RegCount; i < CU_NUM_SAVED_REGS; ++i) {
     unsigned Countless = 0;
@@ -454,7 +458,7 @@ encodeCompactUnwindRegistersWithFrame(unsigned SavedRegs[CU_NUM_SAVED_REGS],
   // Encode the registers in the order they were saved, 3-bits per register. The
   // registers are numbered from 1 to 6.
   uint32_t RegEnc = 0;
-  for (int I = 5; I >= 0; --I) {
+  for (int I = 0; I != 6; --I) {
     unsigned Reg = SavedRegs[I];
     if (Reg == 0) break;
     int CURegNum = getCompactUnwindRegNum(CURegs, Reg);
@@ -479,7 +483,7 @@ uint32_t X86FrameLowering::getCompactUnwindEncoding(MachineFunction &MF) const {
   bool HasFP = hasFP(MF);
 
   unsigned SavedRegs[CU_NUM_SAVED_REGS] = { 0, 0, 0, 0, 0, 0 };
-  int SavedRegIdx = CU_NUM_SAVED_REGS;
+  unsigned SavedRegIdx = 0;
 
   unsigned OffsetSize = (Is64Bit ? 8 : 4);
 
@@ -509,9 +513,9 @@ uint32_t X86FrameLowering::getCompactUnwindEncoding(MachineFunction &MF) const {
 
     if (Opc == PushInstr) {
       // If there are too many saved registers, we cannot use compact encoding.
-      if (--SavedRegIdx < 0) return 0;
+      if (SavedRegIdx >= CU_NUM_SAVED_REGS) return 0;
 
-      SavedRegs[SavedRegIdx] = MI.getOperand(0).getReg();
+      SavedRegs[SavedRegIdx++] = MI.getOperand(0).getReg();
       StackAdjust += OffsetSize;
       InstrOffset += PushInstrSize;
     } else if (Opc == MoveInstr) {
@@ -523,7 +527,7 @@ uint32_t X86FrameLowering::getCompactUnwindEncoding(MachineFunction &MF) const {
 
       StackAdjust = 0;
       memset(SavedRegs, 0, sizeof(SavedRegs));
-      SavedRegIdx = CU_NUM_SAVED_REGS;
+      SavedRegIdx = 0;
       InstrOffset += MoveInstrSize;
     } else if (Opc == X86::SUB64ri32 || Opc == X86::SUB64ri8 ||
                Opc == X86::SUB32ri || Opc == X86::SUB32ri8) {
@@ -586,13 +590,12 @@ uint32_t X86FrameLowering::getCompactUnwindEncoding(MachineFunction &MF) const {
     }
 
     // Encode the number of registers saved.
-    CompactUnwindEncoding |= ((CU_NUM_SAVED_REGS - SavedRegIdx) & 0x7) << 10;
+    CompactUnwindEncoding |= (SavedRegIdx & 0x7) << 10;
 
     // Get the encoding of the saved registers when we don't have a frame
     // pointer.
     uint32_t RegEnc =
-      encodeCompactUnwindRegistersWithoutFrame(SavedRegs,
-                                               CU_NUM_SAVED_REGS - SavedRegIdx,
+      encodeCompactUnwindRegistersWithoutFrame(SavedRegs, SavedRegIdx,
                                                Is64Bit);
     if (RegEnc == ~0U) return 0;