[llvm-commits] [llvm] r146612 - /llvm/trunk/lib/Target/X86/X86FrameLowering.cpp

[Bill Wendling]

Author: void
Date: Wed Dec 14 17:53:24 2011
New Revision: 146612

URL: http://llvm.org/viewvc/llvm-project?rev=146612&view=rev
Log:
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.

Modified:
    llvm/trunk/lib/Target/X86/X86FrameLowering.cpp

Modified: llvm/trunk/lib/Target/X86/X86FrameLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86FrameLowering.cpp?rev=146612&r1=146611&r2=146612&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86FrameLowering.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86FrameLowering.cpp Wed Dec 14 17:53:24 2011
@@ -351,8 +351,7 @@
 /// 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 @@
   };
   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 @@
   // 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 @@
   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 @@
 
     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 @@
 
       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 @@
     }
 
     // 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;