Avoid unneeded SIB byte encoding. Patch by Zoltan Varga.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@71520 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/X86/X86CodeEmitter.cpp b/lib/Target/X86/X86CodeEmitter.cpp
index c21eacc9a4c287bf141084d596c3ded85ec63330..63bf18d157f18b15003e5dae81a0580ff8b2638d 100644 (file)
--- a/lib/Target/X86/X86CodeEmitter.cpp
+++ b/lib/Target/X86/X86CodeEmitter.cpp
@@ -338,7 +338,8 @@ void Emitter::emitMemModRMByte(const MachineInstr &MI,
   unsigned BaseReg = Base.getReg();
 
   // Is a SIB byte needed?
-  if ((!Is64BitMode || DispForReloc) && IndexReg.getReg() == 0 &&
+  if ((!Is64BitMode || DispForReloc || BaseReg != 0) &&
+      IndexReg.getReg() == 0 &&
       (BaseReg == 0 || getX86RegNum(BaseReg) != N86::ESP)) {
     if (BaseReg == 0) {  // Just a displacement?
       // Emit special case [disp32] encoding

diff --git a/lib/Target/X86/X86InstrInfo.cpp b/lib/Target/X86/X86InstrInfo.cpp
index 369c4c6e7e0b023a3db041bccae0554900f723e4..85756a1cdcdd2ab0d98d07acaaf9444962b1e1e9 100644 (file)
--- a/lib/Target/X86/X86InstrInfo.cpp
+++ b/lib/Target/X86/X86InstrInfo.cpp
@@ -2811,7 +2811,8 @@ static unsigned getMemModRMByteSize(const MachineInstr &MI, unsigned Op,
   unsigned BaseReg = Base.getReg();
 
   // Is a SIB byte needed?
-  if ((!Is64BitMode || DispForReloc) && IndexReg.getReg() == 0 &&
+  if ((!Is64BitMode || DispForReloc || BaseReg != 0) &&
+      IndexReg.getReg() == 0 &&
       (BaseReg == 0 || X86RegisterInfo::getX86RegNum(BaseReg) != N86::ESP)) {      
     if (BaseReg == 0) {  // Just a displacement?
       // Emit special case [disp32] encoding