implement (and document!) the first kind of MC assembler alias, which

just remaps one mnemonic to another.  Convert a few of the X86 aliases
from .cpp to .td code.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@117815 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 19 insertions, 0 deletions

diff --git a/include/llvm/Target/Target.td b/include/llvm/Target/Target.td
index 7db2e86..39f4ba7 100644
--- a/include/llvm/Target/Target.td
+++ b/include/llvm/Target/Target.td
@@ -530,6 +530,25 @@ class AsmParser {
 def DefaultAsmParser : AsmParser;
 
 
+/// MnemonicAlias - This class allows targets to define assembler mnemonic
+/// aliases.  This should be used when all forms of one mnemonic are accepted
+/// with a different mnemonic.  For example, X86 allows:
+///   sal %al, 1    -> shl %al, 1
+///   sal %ax, %cl  -> shl %ax, %cl
+///   sal %eax, %cl -> shl %eax, %cl
+/// etc.  Though "sal" is accepted with many forms, all of them are directly
+/// translated to a shl, so it can be handled with (in the case of X86, it
+/// actually has one for each suffix as well):
+///   def : MnemonicAlias<"sal", "shl">;
+///
+/// Mnemonic aliases are mapped before any other translation in the match phase.
+///
+class MnemonicAlias<string From, string To> {
+  string FromMnemonic = From;
+  string ToMnemonic = To;
+}
+
+
 //===----------------------------------------------------------------------===//
 // AsmWriter - This class can be implemented by targets that need to customize
 // the format of the .s file writer.