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[lra] patch to discourage some register usage on x86/x86-64
- From: Vladimir Makarov <vmakarov at redhat dot com>
- To: "gcc-patches at gcc dot gnu dot org" <gcc-patches at gcc dot gnu dot org>
- Date: Mon, 19 Mar 2012 14:48:57 -0400
- Subject: [lra] patch to discourage some register usage on x86/x86-64
The following patch discourages usage of BP, R12, and R13 as it results
in larger addresses on x86/x86-64.
Committed as rev. 185533.
2012-03-19 Vladimir Makarov <vmakarov@redhat.com>
* config/i386/i386.c (ix86_register_bank): Add special treatment
for BP, R12, and R13.
Index: config/i386/i386.c
===================================================================
--- config/i386/i386.c (revision 185531)
+++ config/i386/i386.c (working copy)
@@ -30508,14 +30508,21 @@ ix86_free_from_memory (enum machine_mode
static int
ix86_register_bank (int hard_regno)
{
+ /* ebp and r13 as the base always wants a displacement, r12 as the
+ base always wants an index. So discourage their usage in an
+ address. */
+ if (hard_regno == R12_REG || hard_regno == R13_REG)
+ return 4;
+ if (hard_regno == BP_REG)
+ return 2;
/* New x86-64 int registers result in bigger code size. Discourage
them. */
if (FIRST_REX_INT_REG <= hard_regno && hard_regno <= LAST_REX_INT_REG)
- return 2;
+ return 3;
/* New x86-64 SSE registers result in bigger code size. Discourage
them. */
if (FIRST_REX_SSE_REG <= hard_regno && hard_regno <= LAST_REX_SSE_REG)
- return 2;
+ return 3;
/* Usage of AX register results in smaller code. Prefer it. */
if (hard_regno == 0)
return 0;