[llvm-commits] [llvm] r95693 - in /llvm/trunk: lib/Target/X86/X86CodeEmitter.cpp test/MC/AsmParser/X86/x86_32-encoding.s
Chris Lattner
sabre at nondot.org
Tue Feb 9 13:47:19 PST 2010
Author: lattner
Date: Tue Feb 9 15:47:19 2010
New Revision: 95693
URL: http://llvm.org/viewvc/llvm-project?rev=95693&view=rev
Log:
fix X86 encoder to output [disp] only addresses with no SIB byte
in X86-32 mode. This is still required in x86-64 mode to avoid
forming [disp+rip] encoding. Rewrite the SIB byte decision logic
to be actually understandable.
Modified:
llvm/trunk/lib/Target/X86/X86CodeEmitter.cpp
llvm/trunk/test/MC/AsmParser/X86/x86_32-encoding.s
Modified: llvm/trunk/lib/Target/X86/X86CodeEmitter.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86CodeEmitter.cpp?rev=95693&r1=95692&r2=95693&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86CodeEmitter.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86CodeEmitter.cpp Tue Feb 9 15:47:19 2010
@@ -387,86 +387,98 @@
// If no BaseReg, issue a RIP relative instruction only if the MCE can
// resolve addresses on-the-fly, otherwise use SIB (Intel Manual 2A, table
// 2-7) and absolute references.
- if ((!Is64BitMode || DispForReloc || BaseReg != 0) &&
+ if (// The SIB byte must be used if there is an index register.
IndexReg.getReg() == 0 &&
- ((BaseReg == 0 && MCE.earlyResolveAddresses()) || BaseReg == X86::RIP ||
- (BaseReg != 0 && getX86RegNum(BaseReg) != N86::ESP))) {
- if (BaseReg == 0 || BaseReg == X86::RIP) { // Just a displacement?
- // Emit special case [disp32] encoding
+ // The SIB byte must be used if the base is ESP/RSP.
+ BaseReg != X86::ESP && BaseReg != X86::RSP &&
+ // If there is no base register and we're in 64-bit mode, we need a SIB
+ // byte to emit an addr that is just 'disp32' (the non-RIP relative form).
+ (!Is64BitMode || BaseReg != 0)) {
+ if (BaseReg == 0 || // [disp32] in X86-32 mode
+ BaseReg == X86::RIP) { // [disp32+RIP] in X86-64 mode
MCE.emitByte(ModRMByte(0, RegOpcodeField, 5));
emitDisplacementField(DispForReloc, DispVal, PCAdj, true);
- } else {
- unsigned BaseRegNo = getX86RegNum(BaseReg);
- if (!DispForReloc && DispVal == 0 && BaseRegNo != N86::EBP) {
- // Emit simple indirect register encoding... [EAX] f.e.
- MCE.emitByte(ModRMByte(0, RegOpcodeField, BaseRegNo));
- } else if (!DispForReloc && isDisp8(DispVal)) {
- // Emit the disp8 encoding... [REG+disp8]
- MCE.emitByte(ModRMByte(1, RegOpcodeField, BaseRegNo));
- emitConstant(DispVal, 1);
- } else {
- // Emit the most general non-SIB encoding: [REG+disp32]
- MCE.emitByte(ModRMByte(2, RegOpcodeField, BaseRegNo));
- emitDisplacementField(DispForReloc, DispVal, PCAdj, IsPCRel);
- }
- }
-
- } else { // We need a SIB byte, so start by outputting the ModR/M byte first
- assert(IndexReg.getReg() != X86::ESP &&
- IndexReg.getReg() != X86::RSP && "Cannot use ESP as index reg!");
-
- bool ForceDisp32 = false;
- bool ForceDisp8 = false;
- if (BaseReg == 0) {
- // If there is no base register, we emit the special case SIB byte with
- // MOD=0, BASE=5, to JUST get the index, scale, and displacement.
- MCE.emitByte(ModRMByte(0, RegOpcodeField, 4));
- ForceDisp32 = true;
- } else if (DispForReloc) {
- // Emit the normal disp32 encoding.
- MCE.emitByte(ModRMByte(2, RegOpcodeField, 4));
- ForceDisp32 = true;
- } else if (DispVal == 0 && getX86RegNum(BaseReg) != N86::EBP) {
- // Emit no displacement ModR/M byte
- MCE.emitByte(ModRMByte(0, RegOpcodeField, 4));
- } else if (isDisp8(DispVal)) {
- // Emit the disp8 encoding...
- MCE.emitByte(ModRMByte(1, RegOpcodeField, 4));
- ForceDisp8 = true; // Make sure to force 8 bit disp if Base=EBP
- } else {
- // Emit the normal disp32 encoding...
- MCE.emitByte(ModRMByte(2, RegOpcodeField, 4));
+ return;
}
-
- // Calculate what the SS field value should be...
- static const unsigned SSTable[] = { ~0, 0, 1, ~0, 2, ~0, ~0, ~0, 3 };
- unsigned SS = SSTable[Scale.getImm()];
-
- if (BaseReg == 0) {
- // Handle the SIB byte for the case where there is no base, see Intel
- // Manual 2A, table 2-7. The displacement has already been output.
- unsigned IndexRegNo;
- if (IndexReg.getReg())
- IndexRegNo = getX86RegNum(IndexReg.getReg());
- else // Examples: [ESP+1*<noreg>+4] or [scaled idx]+disp32 (MOD=0,BASE=5)
- IndexRegNo = 4;
- emitSIBByte(SS, IndexRegNo, 5);
- } else {
- unsigned BaseRegNo = getX86RegNum(BaseReg);
- unsigned IndexRegNo;
- if (IndexReg.getReg())
- IndexRegNo = getX86RegNum(IndexReg.getReg());
- else
- IndexRegNo = 4; // For example [ESP+1*<noreg>+4]
- emitSIBByte(SS, IndexRegNo, BaseRegNo);
+
+ unsigned BaseRegNo = getX86RegNum(BaseReg);
+ // If the base is not EBP/ESP and there is no displacement, use simple
+ // indirect register encoding, this handles addresses like [EAX]. The
+ // encoding for [EBP] with no displacement means [disp32] so we handle it
+ // by emitting a displacement of 0 below.
+ if (!DispForReloc && DispVal == 0 && BaseRegNo != N86::EBP) {
+ MCE.emitByte(ModRMByte(0, RegOpcodeField, BaseRegNo));
+ return;
}
-
- // Do we need to output a displacement?
- if (ForceDisp8) {
+
+ // Otherwise, if the displacement fits in a byte, encode as [REG+disp8].
+ if (!DispForReloc && isDisp8(DispVal)) {
+ MCE.emitByte(ModRMByte(1, RegOpcodeField, BaseRegNo));
emitConstant(DispVal, 1);
- } else if (DispVal != 0 || ForceDisp32) {
- emitDisplacementField(DispForReloc, DispVal, PCAdj, IsPCRel);
+ return;
}
+
+ // Otherwise, emit the most general non-SIB encoding: [REG+disp32]
+ MCE.emitByte(ModRMByte(2, RegOpcodeField, BaseRegNo));
+ emitDisplacementField(DispForReloc, DispVal, PCAdj, IsPCRel);
+ return;
+ }
+
+ // Otherwise we need a SIB byte, so start by outputting the ModR/M byte first.
+ assert(IndexReg.getReg() != X86::ESP &&
+ IndexReg.getReg() != X86::RSP && "Cannot use ESP as index reg!");
+
+ bool ForceDisp32 = false;
+ bool ForceDisp8 = false;
+ if (BaseReg == 0) {
+ // If there is no base register, we emit the special case SIB byte with
+ // MOD=0, BASE=4, to JUST get the index, scale, and displacement.
+ MCE.emitByte(ModRMByte(0, RegOpcodeField, 4));
+ ForceDisp32 = true;
+ } else if (DispForReloc) {
+ // Emit the normal disp32 encoding.
+ MCE.emitByte(ModRMByte(2, RegOpcodeField, 4));
+ ForceDisp32 = true;
+ } else if (DispVal == 0 && getX86RegNum(BaseReg) != N86::EBP) {
+ // Emit no displacement ModR/M byte
+ MCE.emitByte(ModRMByte(0, RegOpcodeField, 4));
+ } else if (isDisp8(DispVal)) {
+ // Emit the disp8 encoding...
+ MCE.emitByte(ModRMByte(1, RegOpcodeField, 4));
+ ForceDisp8 = true; // Make sure to force 8 bit disp if Base=EBP
+ } else {
+ // Emit the normal disp32 encoding...
+ MCE.emitByte(ModRMByte(2, RegOpcodeField, 4));
+ }
+
+ // Calculate what the SS field value should be...
+ static const unsigned SSTable[] = { ~0, 0, 1, ~0, 2, ~0, ~0, ~0, 3 };
+ unsigned SS = SSTable[Scale.getImm()];
+
+ if (BaseReg == 0) {
+ // Handle the SIB byte for the case where there is no base, see Intel
+ // Manual 2A, table 2-7. The displacement has already been output.
+ unsigned IndexRegNo;
+ if (IndexReg.getReg())
+ IndexRegNo = getX86RegNum(IndexReg.getReg());
+ else // Examples: [ESP+1*<noreg>+4] or [scaled idx]+disp32 (MOD=0,BASE=5)
+ IndexRegNo = 4;
+ emitSIBByte(SS, IndexRegNo, 5);
+ } else {
+ unsigned BaseRegNo = getX86RegNum(BaseReg);
+ unsigned IndexRegNo;
+ if (IndexReg.getReg())
+ IndexRegNo = getX86RegNum(IndexReg.getReg());
+ else
+ IndexRegNo = 4; // For example [ESP+1*<noreg>+4]
+ emitSIBByte(SS, IndexRegNo, BaseRegNo);
+ }
+
+ // Do we need to output a displacement?
+ if (ForceDisp8) {
+ emitConstant(DispVal, 1);
+ } else if (DispVal != 0 || ForceDisp32) {
+ emitDisplacementField(DispForReloc, DispVal, PCAdj, IsPCRel);
}
}
Modified: llvm/trunk/test/MC/AsmParser/X86/x86_32-encoding.s
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/MC/AsmParser/X86/x86_32-encoding.s?rev=95693&r1=95692&r2=95693&view=diff
==============================================================================
--- llvm/trunk/test/MC/AsmParser/X86/x86_32-encoding.s (original)
+++ llvm/trunk/test/MC/AsmParser/X86/x86_32-encoding.s Tue Feb 9 15:47:19 2010
@@ -4,5 +4,8 @@
# CHECK: encoding: [0xdb,0x8c,0xcb,0xef,0xbe,0xad,0xde]
sbbb $0xfe,0xdeadbeef(%ebx,%ecx,8)
+# CHECK: encoding: [0x80,0x9c,0xcb,0xef,0xbe,0xad,0xde,0xfe]
+
+psllw 69, %mm3
+# CHECK: encoding: [0x0f,0xf1,0x1d,0x45,0x00,0x00,0x00]
-# CHECK: encoding: [0x80,0x9c,0xcb,0xef,0xbe,0xad,0xde,0xfe]
\ No newline at end of file
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