Hi!
This patch adds a few peephole2s to help optimize if (!--*x) etc.
This is something the combiner doesn't and can't easily handle, because in
reg0 = mem1
reg0 {+,-,&,|,^}= x
mem1 = reg0
cc = compare (reg0, 0)
reg0 is used also by both the store and compare and there is no dependence
in between them, so for reg0 = mem1; reg0 {+,-,&,|,^}= x; mem1 = reg0
alone it can't do anything because reg0 is still needed and mem1 {+,-,&,|,^}= x
doesn't set it, and the compare, being second user of reg0, doesn't have any
LOG_LINKS and thus try_combine isn't called for it at all.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2011-05-27 Jakub Jelinek <ja...@redhat.com>
PR rtl-optimization/49095
* config/i386/predicates.md (plusminuslogic_operator): New predicate.
* config/i386/i386.md: Add peepholes for mem {+,-,&,|,^}= x; mem != 0.
* gcc.target/i386/pr49095.c: New test.
--- gcc/config/i386/predicates.md.jj 2011-05-11 19:39:00.000000000 +0200
+++ gcc/config/i386/predicates.md 2011-05-27 10:55:11.000000000 +0200
@@ -1066,6 +1066,10 @@ (define_predicate "mult_operator"
(define_predicate "div_operator"
(match_code "div"))
+;; Return true if this is a plus, minus, and, ior or xor operation.
+(define_predicate "plusminuslogic_operator"
+ (match_code "plus,minus,and,ior,xor"))
+
;; Return true if this is a float extend operation.
(define_predicate "float_operator"
(match_code "float"))
--- gcc/config/i386/i386.md.jj 2011-05-25 16:30:04.000000000 +0200
+++ gcc/config/i386/i386.md 2011-05-27 13:42:11.000000000 +0200
@@ -16852,6 +16852,91 @@ (define_peephole2
(clobber (reg:CC FLAGS_REG))])
(set (match_dup 0) (match_dup 2))])
+;; Attempt to use arith or logical operations with memory outputs with
+;; setting of flags.
+(define_peephole2
+ [(set (match_operand:SWI 0 "register_operand" "")
+ (match_operand:SWI 1 "memory_operand" ""))
+ (parallel [(set (match_dup 0)
+ (match_operator:SWI 3 "plusminuslogic_operator"
+ [(match_dup 0)
+ (match_operand:SWI 2 "<nonmemory_operand>" "")]))
+ (clobber (reg:CC FLAGS_REG))])
+ (set (match_dup 1) (match_dup 0))
+ (set (reg FLAGS_REG) (compare (match_dup 0) (const_int 0)))]
+ "(TARGET_READ_MODIFY_WRITE || optimize_insn_for_size_p ())
+ && peep2_reg_dead_p (4, operands[0])
+ && !reg_overlap_mentioned_p (operands[0], operands[1])
+ && ix86_match_ccmode (peep2_next_insn (3),
+ (GET_CODE (operands[3]) == PLUS
+ || GET_CODE (operands[3]) == MINUS)
+ ? CCGOCmode : CCNOmode)"
+ [(parallel [(set (match_dup 4) (match_dup 5))
+ (set (match_dup 1) (match_op_dup 3 [(match_dup 1)
+ (match_dup 2)]))])]
+ "operands[4] = SET_DEST (PATTERN (peep2_next_insn (3)));
+ operands[5] = gen_rtx_fmt_ee (GET_CODE (operands[3]), <MODE>mode,
+ copy_rtx (operands[1]),
+ copy_rtx (operands[2]));
+ operands[5] = gen_rtx_COMPARE (GET_MODE (operands[4]),
+ operands[5], const0_rtx);")
+
+(define_peephole2
+ [(parallel [(set (match_operand:SWI 0 "register_operand" "")
+ (match_operator:SWI 2 "plusminuslogic_operator"
+ [(match_dup 0)
+ (match_operand:SWI 1 "memory_operand" "")]))
+ (clobber (reg:CC FLAGS_REG))])
+ (set (match_dup 1) (match_dup 0))
+ (set (reg FLAGS_REG) (compare (match_dup 0) (const_int 0)))]
+ "(TARGET_READ_MODIFY_WRITE || optimize_insn_for_size_p ())
+ && GET_CODE (operands[2]) != MINUS
+ && peep2_reg_dead_p (3, operands[0])
+ && !reg_overlap_mentioned_p (operands[0], operands[1])
+ && ix86_match_ccmode (peep2_next_insn (2),
+ GET_CODE (operands[2]) == PLUS
+ ? CCGOCmode : CCNOmode)"
+ [(parallel [(set (match_dup 3) (match_dup 4))
+ (set (match_dup 1) (match_op_dup 2 [(match_dup 1)
+ (match_dup 0)]))])]
+ "operands[3] = SET_DEST (PATTERN (peep2_next_insn (2)));
+ operands[4] = gen_rtx_fmt_ee (GET_CODE (operands[2]), <MODE>mode,
+ copy_rtx (operands[1]),
+ copy_rtx (operands[0]));
+ operands[4] = gen_rtx_COMPARE (GET_MODE (operands[3]),
+ operands[4], const0_rtx);")
+
+(define_peephole2
+ [(set (match_operand:SWI12 0 "register_operand" "")
+ (match_operand:SWI12 1 "memory_operand" ""))
+ (parallel [(set (match_operand:SI 4 "register_operand" "")
+ (match_operator:SI 3 "plusminuslogic_operator"
+ [(match_dup 4)
+ (match_operand:SI 2 "nonmemory_operand" "")]))
+ (clobber (reg:CC FLAGS_REG))])
+ (set (match_dup 1) (match_dup 0))
+ (set (reg FLAGS_REG) (compare (match_dup 0) (const_int 0)))]
+ "(TARGET_READ_MODIFY_WRITE || optimize_insn_for_size_p ())
+ && REG_P (operands[0]) && REG_P (operands[4])
+ && REGNO (operands[0]) == REGNO (operands[4])
+ && peep2_reg_dead_p (4, operands[0])
+ && !reg_overlap_mentioned_p (operands[0], operands[1])
+ && ix86_match_ccmode (peep2_next_insn (3),
+ (GET_CODE (operands[3]) == PLUS
+ || GET_CODE (operands[3]) == MINUS)
+ ? CCGOCmode : CCNOmode)"
+ [(parallel [(set (match_dup 4) (match_dup 5))
+ (set (match_dup 1) (match_dup 6))])]
+ "operands[2] = gen_lowpart (<MODE>mode, operands[2]);
+ operands[4] = SET_DEST (PATTERN (peep2_next_insn (3)));
+ operands[5] = gen_rtx_fmt_ee (GET_CODE (operands[3]), <MODE>mode,
+ copy_rtx (operands[1]), operands[2]);
+ operands[5] = gen_rtx_COMPARE (GET_MODE (operands[4]),
+ operands[5], const0_rtx);
+ operands[6] = gen_rtx_fmt_ee (GET_CODE (operands[3]), <MODE>mode,
+ copy_rtx (operands[1]),
+ copy_rtx (operands[2]));")
+
;; Attempt to always use XOR for zeroing registers.
(define_peephole2
[(set (match_operand 0 "register_operand" "")
--- gcc/testsuite/gcc.target/i386/pr49095.c.jj 2011-05-27 12:10:39.000000000
+0200
+++ gcc/testsuite/gcc.target/i386/pr49095.c 2011-05-27 13:50:24.000000000
+0200
@@ -0,0 +1,73 @@
+/* PR rtl-optimization/49095 */
+/* { dg-do compile } */
+/* { dg-options "-Os" } */
+/* { dg-options "-Os -mregparm=2" { target ilp32 } } */
+
+void foo (void *);
+
+int *
+f1 (int *x)
+{
+ if (!--*x)
+ foo (x);
+ return x;
+}
+
+int
+g1 (int x)
+{
+ if (!--x)
+ foo ((void *) 0);
+ return x;
+}
+
+#define F(T, OP, OPN) \
+T * \
+f##T##OPN (T *x, T y) \
+{ \
+ *x OP y; \
+ if (!*x) \
+ foo (x); \
+ return x; \
+} \
+ \
+T \
+g##T##OPN (T x, T y) \
+{ \
+ x OP y; \
+ if (!x) \
+ foo ((void *) 0); \
+ return x; \
+} \
+ \
+T * \
+h##T##OPN (T *x) \
+{ \
+ *x OP 24; \
+ if (!*x) \
+ foo (x); \
+ return x; \
+} \
+ \
+T \
+i##T##OPN (T x, T y) \
+{ \
+ x OP 24; \
+ if (!x) \
+ foo ((void *) 0); \
+ return x; \
+}
+
+#define G(T) \
+F (T, +=, plus) \
+F (T, -=, minus) \
+F (T, &=, and) \
+F (T, |=, or) \
+F (T, ^=, xor)
+
+G (char)
+G (short)
+G (int)
+G (long)
+
+/* { dg-final { scan-assembler-not "test\[lq\]" } } */
Jakub
