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sketch out the planned instruction alias mechanism, add some comments about

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how the push/pop mnemonic aliases are wrong.

llvm-svn: 117857
This commit is contained in:
Chris Lattner 2010-10-31 18:43:46 +00:00
parent 92f33ea784
commit 8aaac91ca4
2 changed files with 26 additions and 0 deletions
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12
include/llvm/Target/Target.td
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@ -567,6 +567,18 @@ class MnemonicAlias<string From, string To> {
list<Predicate> Predicates = [];
}
/// InstAlias - This defines an alternate assembly syntax that is allowed to
/// match an instruction that has a different (more canonical) assembly
/// representation.
class InstAlias<dag Outs, dag Ins, string Asm, dag Result> {
dag OutOperandList = Outs; // An dag containing the MI def operand list.
dag InOperandList = Ins; // An dag containing the MI use operand list.
string AsmString = Asm; // The .s format to match the instruction with.
dag ResultInst = Result; // The MCInst to generate.
// Predicates - Predicates that must be true for this to match.
list<Predicate> Predicates = [];
}
//===----------------------------------------------------------------------===//
// AsmWriter - This class can be implemented by targets that need to customize

14
lib/Target/X86/X86InstrInfo.td
View File

@ -1258,6 +1258,17 @@ include "X86InstrCompiler.td"
// Assembler Aliases
//===----------------------------------------------------------------------===//
// movsx aliases
def : InstAlias<(outs GR32:$dst), (ins GR8 :$src),
"movsx $src, $dst",
(MOVSX32rr8 GR32:$dst, GR8:$src)>;
def : InstAlias<(outs GR32:$dst), (ins GR16:$src),
"movsx $src, $dst",
(MOVSX32rr16 GR32:$dst, GR16:$src)>;
// TODO: lidtl/lidtq can be opcode aliases, perhaps others.
def : MnemonicAlias<"iret", "iretl">;
def : MnemonicAlias<"sysret", "sysretl">;
def : MnemonicAlias<"cbw", "cbtw">;
@ -1272,6 +1283,9 @@ def : MnemonicAlias<"popf", "popfl">, Requires<[In32BitMode]>;
def : MnemonicAlias<"popf", "popfq">, Requires<[In64BitMode]>;
def : MnemonicAlias<"popfd", "popfl">;
// FIXME: This is wrong for "push reg". "push %bx" should turn into pushw in
// all modes. However: "push (addr)" and "push $42" should default to
// pushl/pushq depending on the current mode. Similar for "pop %bx"
def : MnemonicAlias<"push", "pushl">, Requires<[In32BitMode]>;
def : MnemonicAlias<"push", "pushq">, Requires<[In64BitMode]>;
def : MnemonicAlias<"pushf", "pushfl">, Requires<[In32BitMode]>;