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authorJan Beulich <jbeulich@suse.com>2021-03-29 12:03:31 +0200
committerJan Beulich <jbeulich@suse.com>2021-03-29 12:03:31 +0200
commit9df6f676c2c7280dc0c419c43927a07c6359814d (patch)
treeebc12d8d2d39793ca514b4f004494a17c5a6710f
parent389d00a5e5b1fa6fcd9eda747b17ef73f58eb693 (diff)
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x86: shrink some struct insn_template fields
Now that all base opcodes are only at most 2 bytes in size, shrink its template field to just as much. By also shrinking extension_opcode and operands to just what they really need, we can free up an entire 32-bit slot (plus 4 left bits past the bitfields themselves). At present this alters sizeof(struct insn_template) only for 32-bit builds. In 64-bit builds it instead leaves a padding hole that will allow to buffer future growth of other fields (opcode_modifier, cpu_flags, operand_types[]).
-rw-r--r--opcodes/ChangeLog6
-rw-r--r--opcodes/i386-opc.h8
2 files changed, 10 insertions, 4 deletions
diff --git a/opcodes/ChangeLog b/opcodes/ChangeLog
index 82a1c5c..ff0ecf3 100644
--- a/opcodes/ChangeLog
+++ b/opcodes/ChangeLog
@@ -1,5 +1,11 @@
2021-03-29 Jan Beulich <jbeulich@suse.com>
+ * i386-opc.h (struct insn_template): Shrink base_opcode to 16
+ bits. Shrink extension_opcode to 9 bits. Make it signed. Change
+ value of None. Shrink operands to 3 bits.
+
+2021-03-29 Jan Beulich <jbeulich@suse.com>
+
* i386-gen.c (process_i386_opcode_modifier): New parameter
"space".
(output_i386_opcode): New local variable "space". Adjust
diff --git a/opcodes/i386-opc.h b/opcodes/i386-opc.h
index 9ed0793..115895c 100644
--- a/opcodes/i386-opc.h
+++ b/opcodes/i386-opc.h
@@ -917,7 +917,7 @@ typedef struct insn_template
/* base_opcode is the fundamental opcode byte without optional
prefix(es). */
- unsigned int base_opcode;
+ unsigned int base_opcode:16;
#define Opcode_D 0x2 /* Direction bit:
set if Reg --> Regmem;
unset if Regmem --> Reg. */
@@ -934,8 +934,8 @@ typedef struct insn_template
AMD 3DNow! instructions.
If this template has no extension opcode (the usual case) use None
Instructions */
- unsigned short extension_opcode;
-#define None 0xffff /* If no extension_opcode is possible. */
+ signed int extension_opcode:9;
+#define None (-1) /* If no extension_opcode is possible. */
/* Pseudo prefixes. */
#define Prefix_Disp8 0 /* {disp8} */
@@ -950,7 +950,7 @@ typedef struct insn_template
#define Prefix_NoOptimize 9 /* {nooptimize} */
/* how many operands */
- unsigned char operands;
+ unsigned int operands:3;
/* the bits in opcode_modifier are used to generate the final opcode from
the base_opcode. These bits also are used to detect alternate forms of