From aa8a1c835b392023d2551257ee02951e43ee27db Mon Sep 17 00:00:00 2001
From: Michael Forney <mforney@mforney.org>
Date: Tue, 19 Oct 2021 13:44:45 -0700
Subject: Use small immediates when possible for imul.

---
 asm.peg      | 12 ++++++------
 test/test.sh |  1 +
 2 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/asm.peg b/asm.peg
index 401c56b..4cabefa 100644
--- a/asm.peg
+++ b/asm.peg
@@ -256,13 +256,13 @@ imul = "imul" (
   | 'l'? ws s:mem ws? ',' ws? d:r32 { $$ = MEMREG({.w=0},   -1, 0x01000faf, s, d); }
   | 'q'? ws s:mem ws? ',' ws? d:r64 { $$ = MEMREG({.w=1},   -1, 0x01000faf, s, d); }
   
-  | 'w'? ws i:imm16 ws? ',' ws? s:r16 ws? ',' ws? d:r16 { $$ = IMMREGREG2({.w=0}, 0x66, 0x69, i, s, d); }
-  | 'l'? ws i:imm32 ws? ',' ws? s:r32 ws? ',' ws? d:r32 { $$ = IMMREGREG2({.w=0},   -1, 0x69, i, s, d); }
-  | 'q'? ws i:imm32 ws? ',' ws? s:r64 ws? ',' ws? d:r64 { $$ = IMMREGREG2({.w=1},   -1, 0x69, i, s, d); }
+  | 'w'? ws i:imm16-8 ws? ',' ws? s:r16 ws? ',' ws? d:r16 { $$ = IMMREGREG2({.w=0}, 0x66, i.imm.nbytes == 1 ? 0x6b : 0x69, i, s, d); }
+  | 'l'? ws i:imm32-8 ws? ',' ws? s:r32 ws? ',' ws? d:r32 { $$ = IMMREGREG2({.w=0},   -1, i.imm.nbytes == 1 ? 0x6b : 0x69, i, s, d); }
+  | 'q'? ws i:imm32-8 ws? ',' ws? s:r64 ws? ',' ws? d:r64 { $$ = IMMREGREG2({.w=1},   -1, i.imm.nbytes == 1 ? 0x6b : 0x69, i, s, d); }
   
-  | 'w'? ws i:imm16 ws? ',' ws? s:mem ws? ',' ws? d:r16 { $$ = IMMMEMREG({.w=0}, 0x66, 0x69, i, s, d); }
-  | 'l'? ws i:imm32 ws? ',' ws? s:mem ws? ',' ws? d:r32 { $$ = IMMMEMREG({.w=0},   -1, 0x69, i, s, d); }
-  | 'q'? ws i:imm32 ws? ',' ws? s:mem ws? ',' ws? d:r64 { $$ = IMMMEMREG({.w=1},   -1, 0x69, i, s, d); }
+  | 'w'? ws i:imm16-8 ws? ',' ws? s:mem ws? ',' ws? d:r16 { $$ = IMMMEMREG({.w=0}, 0x66, i.imm.nbytes == 1 ? 0x6b : 0x69, i, s, d); }
+  | 'l'? ws i:imm32-8 ws? ',' ws? s:mem ws? ',' ws? d:r32 { $$ = IMMMEMREG({.w=0},   -1, i.imm.nbytes == 1 ? 0x6b : 0x69, i, s, d); }
+  | 'q'? ws i:imm32-8 ws? ',' ws? s:mem ws? ',' ws? d:r64 { $$ = IMMMEMREG({.w=1},   -1, i.imm.nbytes == 1 ? 0x6b : 0x69, i, s, d); }
   
   # Must come last due to peg ordering.
   | 'b'  ws a:mem { $$ = OPMEM({.w=0},   -1, 0xf6, 0x05, a); }
diff --git a/test/test.sh b/test/test.sh
index ecf5ce1..5536d61 100644
--- a/test/test.sh
+++ b/test/test.sh
@@ -44,6 +44,7 @@ t "callq *%r10"
 t "callq *(%r10)"
 t "movb %r11b, (%rsi, %r12, 1)"
 t "mov %rdi, -0x60(%rbp)"
+t "imul \$0x28, %rbx, %rcx"
 
 for r in rax r10
 do
-- 
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