[x86] Fix retq/retl handling in 64-bit mode

This finishes the job started in r198756, and creates separate opcodes for
64-bit vs. 32-bit versions of the rest of the RET instructions too.

LRETL/LRETQ are interesting... I can't see any justification for their
existence in the SDM. There should be no 'LRETL' in 64-bit mode, and no
need for a REX.W prefix for LRETQ. But this is what GAS does, and my
Sandybridge CPU and an Opteron 6376 concur when tested as follows:

asm __volatile__("pushq $0x1234\nmovq $0x33,%rax\nsalq $32,%rax\norq $1f,%rax\npushq %rax\nlretl $8\n1:");
asm __volatile__("pushq $1234\npushq $0x33\npushq $1f\nlretq $8\n1:");
asm __volatile__("pushq $0x33\npushq $1f\nlretq\n1:");
asm __volatile__("pushq $0x1234\npushq $0x33\npushq $1f\nlretq $8\n1:");

cf. PR8592 and commit r118903, which added LRETQ. I only added LRETIQ to
match it.

I don't quite understand how the Intel syntax parsing for ret
instructions is working, despite r154468 allegedly fixing it. Aren't the
explicitly sized 'retw', 'retd' and 'retq' supposed to work? I have at
least made the 'lretq' work with (and indeed *require*) the 'q'.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199106 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 1 insertions, 1 deletions

diff --git a/lib/Target/X86/X86InstrInfo.td b/lib/Target/X86/X86InstrInfo.td
index bfa59ea9df..1681ad7a5e 100644
--- a/lib/Target/X86/X86InstrInfo.td
+++ b/lib/Target/X86/X86InstrInfo.td
@@ -2162,7 +2162,7 @@ def : MnemonicAlias<"cdq",  "cltd", "att">;
 def : MnemonicAlias<"cdqe", "cltq", "att">;
 def : MnemonicAlias<"cqo",  "cqto", "att">;
 
-// lret maps to lretl, it is not ambiguous with lretq.
+// In 64-bit mode lret maps to lretl; it is not ambiguous with lretq.
 def : MnemonicAlias<"lret", "lretw", "att">, Requires<[In16BitMode]>;
 def : MnemonicAlias<"lret", "lretl", "att">, Requires<[Not16BitMode]>;