Hello!
Attached patch introduces generation of addr32 prefixed addresses,
mainly intended to merge ZERO_EXTRACTed LEA calculations into address.
After fixing various inconsistencies with "o" constraints, the patch
works surprisingly well (in its current form fixes all reported
problems in the PR [1]), but one problem remains w.r.t. handling of
"o" constraint.
Patched gcc ICEs on gcc.dg/torture/pr47744-2.c with:
$ ~/gcc-build-fast/gcc/cc1 -O2 -mx32 -std=gnu99 -quiet pr47744-2.c
pr47744-2.c: In function ‘matmul_i16’:
pr47744-2.c:40:1: error: insn does not satisfy its constraints:
(insn 116 66 67 4 (set (reg:TI 0 ax)
(mem:TI (zero_extend:DI (plus:SI (reg:SI 4 si [orig:114
ivtmp.26 ] [114])
(reg:SI 5 di [orig:101 dest_y ] [101]))) [6
MEM[base: dest_y_18, index: ivtmp.26_53, offset: 0B]+0 S16 A128]))
pr47744-2.c:34 60 {*movti_internal_rex64}
(nil))
pr47744-2.c:40:1: internal compiler error: in
reload_cse_simplify_operands, at postreload.c:403
Please submit a full bug report,
...
... due to the fact that the address is not offsetable, and plus
((zero_extend (...)) (const_int ...)) gets rejected from
ix86_legitimate_address_p.
However, the section "16.8.1 Simple Constraints" of the documentation claims:
--quote--
* A nonoffsettable memory reference can be reloaded by copying the
address into a register. So if the constraint uses the letter
`o', all memory references are taken care of.
--/quote--
As I read this sentence, the RTX is forced into a temporary register,
and reload tries to satisfy "o" constraint with plus ((reg ...)
(const_int ...)), as said at the introduction of "o" constraint a
couple of pages earlier. Unfortunately, this does not seem to be the
case.
Is there anything wrong with my approach, or is there something wrong in reload?
2011-08-05 Uros Bizjak <ubiz...@gmail.com>
PR target/49781
* config/i386/i386.c (ix86_decompose_address): Allow zero-extended
SImode addresses.
(ix86_print_operand_address): Handle zero-extended addresses.
(memory_address_length): Add length of addr32 prefix for
zero-extended addresses.
* config/i386/predicates.md (lea_address_operand): Reject
zero-extended operands.
Patch is otherwise bootstrapped and tested on x86_64-pc-linux-gnu
{,-m32} without regressions.
[1] http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49781
Thanks,
Uros.
Index: config/i386/predicates.md
===================================================================
--- config/i386/predicates.md (revision 177456)
+++ config/i386/predicates.md (working copy)
@@ -801,6 +801,10 @@
struct ix86_address parts;
int ok;
+ /* LEA handles zero-extend by itself. */
+ if (GET_CODE (op) == ZERO_EXTEND)
+ return false;
+
ok = ix86_decompose_address (op, &parts);
gcc_assert (ok);
return parts.seg == SEG_DEFAULT;
Index: config/i386/i386.c
===================================================================
--- config/i386/i386.c (revision 177456)
+++ config/i386/i386.c (working copy)
@@ -11146,6 +11146,14 @@ ix86_decompose_address (rtx addr, struct ix86_addr
int retval = 1;
enum ix86_address_seg seg = SEG_DEFAULT;
+ /* Allow zero-extended SImode addresses,
+ they will be emitted with addr32 prefix. */
+ if (TARGET_64BIT
+ && GET_CODE (addr) == ZERO_EXTEND
+ && GET_MODE (addr) == DImode
+ && GET_MODE (XEXP (addr, 0)) == SImode)
+ addr = XEXP (addr, 0);
+
if (REG_P (addr))
base = addr;
else if (GET_CODE (addr) == SUBREG)
@@ -14163,9 +14171,13 @@ ix86_print_operand_address (FILE *file, rtx addr)
}
else
{
- /* Print DImode registers on 64bit targets to avoid addr32 prefixes. */
- int code = TARGET_64BIT ? 'q' : 0;
+ int code = 0;
+ /* Print SImode registers for zero-extended addresses to force
+ addr32 prefix. Otherwise print DImode registers to avoid it. */
+ if (TARGET_64BIT)
+ code = (GET_CODE (addr) == ZERO_EXTEND) ? 'l' : 'q';
+
if (ASSEMBLER_DIALECT == ASM_ATT)
{
if (disp)
@@ -21776,7 +21788,8 @@ assign_386_stack_local (enum machine_mode mode, en
}
/* Calculate the length of the memory address in the instruction
- encoding. Does not include the one-byte modrm, opcode, or prefix. */
+ encoding. Includes addr32 prefix, does not include the one-byte modrm,
+ opcode, or other prefixes. */
int
memory_address_length (rtx addr)
@@ -21803,8 +21816,10 @@ memory_address_length (rtx addr)
base = parts.base;
index = parts.index;
disp = parts.disp;
- len = 0;
+ /* Add length of addr32 prefix. */
+ len = (GET_CODE (addr) == ZERO_EXTEND);
+
/* Rule of thumb:
- esp as the base always wants an index,
- ebp as the base always wants a displacement,
