Hi!
Since r247992 the cmpelim pass optimizes a few arithmetics with following
comparisons and some of the peephole2s we have to recognize RMW instructions
with comparisons don't trigger anymore.
In particular, on the pr49095.c testcase in GCC 7 only 8 functions used
load + comparison with arith + store ([fh]*xor, something to look at later),
while in GCC 8/9 21 further functions do that. This patch restores it to
the GCC 7 counts.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
What about GCC 8.2?
2018-05-08 Jakub Jelinek <ja...@redhat.com>
PR target/85683
* config/i386/i386.md: Add peepholes for mem {+,-,&,|,^}= x; mem != 0
after cmpelim optimization.
* gcc.target/i386/pr49095.c: Add -masm=att to dg-options. Add
scan-assembler-times checking that except for [fh]*xor other functions
don't use any load instructions.
--- gcc/config/i386/i386.md.jj 2018-05-02 23:55:44.000000000 +0200
+++ gcc/config/i386/i386.md 2018-05-08 10:39:52.691422990 +0200
@@ -19285,6 +19285,37 @@ (define_peephole2
const0_rtx);
})
+;; Likewise for cmpelim optimized pattern.
+(define_peephole2
+ [(set (match_operand:SWI 0 "register_operand")
+ (match_operand:SWI 1 "memory_operand"))
+ (parallel [(set (reg FLAGS_REG)
+ (compare (match_operator:SWI 3 "plusminuslogic_operator"
+ [(match_dup 0)
+ (match_operand:SWI 2 "<nonmemory_operand>")])
+ (const_int 0)))
+ (set (match_dup 0) (match_dup 3))])
+ (set (match_dup 1) (match_dup 0))]
+ "(TARGET_READ_MODIFY_WRITE || optimize_insn_for_size_p ())
+ && peep2_reg_dead_p (3, operands[0])
+ && !reg_overlap_mentioned_p (operands[0], operands[1])
+ && !reg_overlap_mentioned_p (operands[0], operands[2])
+ && ix86_match_ccmode (peep2_next_insn (1),
+ (GET_CODE (operands[3]) == PLUS
+ || GET_CODE (operands[3]) == MINUS)
+ ? CCGOCmode : CCNOmode)"
+ [(parallel [(set (match_dup 4) (match_dup 6))
+ (set (match_dup 1) (match_dup 5))])]
+{
+ operands[4] = SET_DEST (XVECEXP (PATTERN (peep2_next_insn (1)), 0, 0));
+ operands[5]
+ = gen_rtx_fmt_ee (GET_CODE (operands[3]), GET_MODE (operands[3]),
+ copy_rtx (operands[1]), operands[2]);
+ operands[6]
+ = gen_rtx_COMPARE (GET_MODE (operands[4]), copy_rtx (operands[5]),
+ const0_rtx);
+})
+
;; Likewise for instances where we have a lea pattern.
(define_peephole2
[(set (match_operand:SWI 0 "register_operand")
@@ -19348,6 +19379,34 @@ (define_peephole2
const0_rtx);
})
+;; Likewise for cmpelim optimized pattern.
+(define_peephole2
+ [(parallel [(set (reg FLAGS_REG)
+ (compare (match_operator:SWI 2 "plusminuslogic_operator"
+ [(match_operand:SWI 0 "register_operand")
+ (match_operand:SWI 1 "memory_operand")])
+ (const_int 0)))
+ (set (match_dup 0) (match_dup 2))])
+ (set (match_dup 1) (match_dup 0))]
+ "(TARGET_READ_MODIFY_WRITE || optimize_insn_for_size_p ())
+ && peep2_reg_dead_p (2, operands[0])
+ && !reg_overlap_mentioned_p (operands[0], operands[1])
+ && ix86_match_ccmode (peep2_next_insn (0),
+ (GET_CODE (operands[2]) == PLUS
+ || GET_CODE (operands[2]) == MINUS)
+ ? CCGOCmode : CCNOmode)"
+ [(parallel [(set (match_dup 3) (match_dup 5))
+ (set (match_dup 1) (match_dup 4))])]
+{
+ operands[3] = SET_DEST (XVECEXP (PATTERN (peep2_next_insn (0)), 0, 0));
+ operands[4]
+ = gen_rtx_fmt_ee (GET_CODE (operands[2]), GET_MODE (operands[2]),
+ copy_rtx (operands[1]), operands[0]);
+ operands[5]
+ = gen_rtx_COMPARE (GET_MODE (operands[3]), copy_rtx (operands[4]),
+ const0_rtx);
+})
+
(define_peephole2
[(set (match_operand:SWI12 0 "register_operand")
(match_operand:SWI12 1 "memory_operand"))
--- gcc/testsuite/gcc.target/i386/pr49095.c.jj 2017-02-14 20:34:47.575579410
+0100
+++ gcc/testsuite/gcc.target/i386/pr49095.c 2018-05-08 10:52:03.781730062
+0200
@@ -1,6 +1,6 @@
/* PR rtl-optimization/49095 */
/* { dg-do compile } */
-/* { dg-options "-Os -fno-shrink-wrap" } */
+/* { dg-options "-Os -fno-shrink-wrap -masm=att" } */
/* { dg-additional-options "-mregparm=2" { target ia32 } } */
void foo (void *);
@@ -71,3 +71,6 @@ G (int)
G (long)
/* { dg-final { scan-assembler-not "test\[lq\]" } } */
+/* The {f,h}{char,short,int,long}xor functions aren't optimized into
+ a RMW instruction, so need load, modify and store. FIXME eventually. */
+/* { dg-final { scan-assembler-times "\\), %" 8 } } */
Jakub
