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Doubleword version of and;cmp to not;test optimization on x86.

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This patch extends the earlier and;cmp to not;test optimization to also
perform this transformation for TImode on TARGET_64BIT and DImode on -m32,
One motivation for this is that it's a step to fixing the current failure
of gcc.target/i386/pr65105-5.c on -m32.

A more direct benefit for x86_64 is that the following code:

int foo(__int128 x, __int128 y)
{
  return (x & y) == y;
}

improves with -O2 from 15 instructions:

        movq    %rdi, %r8
        movq    %rsi, %rax
        movq    %rax, %rdi
        movq    %r8, %rsi
        movq    %rdx, %r8
        andq    %rdx, %rsi
        andq    %rcx, %rdi
        movq    %rsi, %rax
        movq    %rdi, %rdx
        xorq    %r8, %rax
        xorq    %rcx, %rdx
        orq     %rdx, %rax
        sete    %al
        movzbl  %al, %eax
        ret

to the slightly better 13 instructions:

        movq    %rdi, %r8
        movq    %rsi, %rax
        movq    %r8, %rsi
        movq    %rax, %rdi
        notq    %rsi
        notq    %rdi
        andq    %rdx, %rsi
        andq    %rcx, %rdi
        movq    %rsi, %rax
        orq     %rdi, %rax
        sete    %al
        movzbl  %al, %eax
        ret

2022-07-05  Roger Sayle  <roger@nextmovesoftware.com>

gcc/ChangeLog
	* config/i386/i386.cc (ix86_rtx_costs) <COMPARE>: Provide costs
	for double word comparisons and tests (comparisons against zero).
	* config/i386/i386.md (*test<mode>_not_doubleword): Split DWI
	and;cmp into andn;cmp $0 as a pre-reload splitter.
	(*andn<dwi>3_doubleword_bmi): Use <dwi> instead of <mode> in name.
	(*<any_or><dwi>3_doubleword): Likewise.

gcc/testsuite/ChangeLog
	* gcc.target/i386/testnot-3.c: New test case.
This commit is contained in:
Roger Sayle 2022-07-05 18:06:13 +01:00
parent 02e2e15ec4
commit c73e8d45ca
3 changed files with 42 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
gcc/config/i386/i386.cc
View File

@ -20982,6 +20982,19 @@ ix86_rtx_costs (rtx x, machine_mode mode, int outer_code_i, int opno,
return true;
}
if (SCALAR_INT_MODE_P (GET_MODE (op0))
&& GET_MODE_SIZE (GET_MODE (op0)) > UNITS_PER_WORD)
{
if (op1 == const0_rtx)
*total = cost->add
+ rtx_cost (op0, GET_MODE (op0), outer_code, opno, speed);
else
*total = 3*cost->add
+ rtx_cost (op0, GET_MODE (op0), outer_code, opno, speed)
+ rtx_cost (op1, GET_MODE (op0), outer_code, opno, speed);
return true;
}
/* The embedded comparison operand is completely free. */
if (!general_operand (op0, GET_MODE (op0)) && op1 == const0_rtx)
*total = 0;

22
gcc/config/i386/i386.md
View File

@ -9792,7 +9792,25 @@
(set (reg:CCZ FLAGS_REG)
(compare:CCZ (and:SWI (match_dup 2) (match_dup 1))
(const_int 0)))]
"operands[2] = gen_reg_rtx (<MODE>mode);")
;; Split and;cmp (as optimized by combine) into andn;cmp $0
(define_insn_and_split "*test<mode>_not_doubleword"
[(set (reg:CCZ FLAGS_REG)
(compare:CCZ
(and:DWI
(not:DWI (match_operand:DWI 0 "nonimmediate_operand"))
(match_operand:DWI 1 "nonimmediate_operand"))
(const_int 0)))]
"ix86_pre_reload_split ()"
"#"
"&& 1"
[(parallel
[(set (match_dup 2) (and:DWI (not:DWI (match_dup 0)) (match_dup 1)))
(clobber (reg:CC FLAGS_REG))])
(set (reg:CCZ FLAGS_REG) (compare:CCZ (match_dup 2) (const_int 0)))]
{
operands[0] = force_reg (<MODE>mode, operands[0]);
operands[2] = gen_reg_rtx (<MODE>mode);
})
@ -10404,7 +10422,7 @@
operands[2] = gen_int_mode (INTVAL (operands[2]), QImode);
})
(define_insn_and_split "*andn<mode>3_doubleword_bmi"
(define_insn_and_split "*andn<dwi>3_doubleword_bmi"
[(set (match_operand:<DWI> 0 "register_operand" "=r")
(and:<DWI>
(not:<DWI> (match_operand:<DWI> 1 "register_operand" "r"))
@ -10618,7 +10636,7 @@
DONE;
})
(define_insn_and_split "*<code><mode>3_doubleword"
(define_insn_and_split "*<code><dwi>3_doubleword"
[(set (match_operand:<DWI> 0 "nonimmediate_operand" "=ro,r")
(any_or:<DWI>
(match_operand:<DWI> 1 "nonimmediate_operand" "%0,0")

9
gcc/testsuite/gcc.target/i386/testnot-3.c Normal file
View File

@ -0,0 +1,9 @@
/* { dg-do compile { target int128 } } */
/* { dg-options "-O2" } */
int foo(__int128 x, __int128 y)
{
return (x & y) == y;
}
/* { dg-final { scan-assembler-not "xorq" } } */