@@ -18118,6 +18118,35 @@ (define_split
FAIL;
})
+;; Eliminate redundant compare between set{z,nz} and j{z,nz}:
+;; setz %al; test %al,%al; jz <...> -> setz %al; jnz <...> and
+;; setnz %al, test %al,%al; jz <...> -> setnz %al; jz <...>.
+(define_peephole2
+ [(set (match_operand:QI 0 "nonimmediate_operand")
+ (match_operator:QI 1 "bt_comparison_operator"
+ [(reg:CCZ FLAGS_REG) (const_int 0)]))
+ (set (reg:CCZ FLAGS_REG)
+ (compare:CCZ (match_dup 0) (const_int 0)))
+ (set (pc)
+ (if_then_else (match_operator 2 "bt_comparison_operator"
+ [(reg:CCZ FLAGS_REG) (const_int 0)])
+ (match_operand 3)
+ (pc)))]
+ "peep2_regno_dead_p (3, FLAGS_REG)"
+ [(set (match_dup 0)
+ (match_op_dup 1 [(reg:CCZ FLAGS_REG) (const_int 0)]))
+ (set (pc)
+ (if_then_else (match_dup 2)
+ (match_dup 3)
+ (pc)))]
+{
+ if (GET_CODE (operands[1]) == EQ)
+ {
+ operands[2] = shallow_copy_rtx (operands[2]);
+ PUT_CODE (operands[2], reverse_condition (GET_CODE (operands[2])));
+ }
+})
+
;; The SSE store flag instructions saves 0 or 0xffffffff to the result.
;; subsequent logical operations are used to imitate conditional moves.
;; 0xffffffff is NaN, but not in normalized form, so we can't represent
Eliminate redundant compare between set{z,nz} and j{z,nz}: setz %al; test %al,%al; jz <...> -> setz %al; jnz <...> and setnz %al, test %al,%al; jz <...> -> setnz %al; jz <...>. We can use the original Zero-flag value instead of setting the temporary register and testing it for zero. gcc/ChangeLog: * config/i386/i386.md (redundant compare peephole2): New peephole2 pattern. Bootstrapped and regression tested on x86_64-linux-gnu {,-m32}. Also tested by building and booting the linux kernel (where the peephole2 triggers several times). I was not able to craft the testcase, the original sequence is very elusive and requires reuse of the value, set from the flags elsewhere in the function in a very specific way. Uros.