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aarch64: Emit csinv again for a ? ~b : b [PR110986]
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After r14-3110-g7fb65f10285, the canonical form for
`a ? ~b : b` changed to be `-(a) ^ b` that means
for aarch64 we need to add a few new insn patterns
to be able to catch this and change it to be
what is the canonical form for the aarch64 backend.
A secondary pattern was needed to support a zero_extended
form too; this adds a testcase for all 3 cases.

Bootstrapped and tested on aarch64-linux-gnu with no regressions.

	PR target/110986

gcc/ChangeLog:

	* config/aarch64/aarch64.md (*cmov<mode>_insn_insv): New pattern.
	(*cmov_uxtw_insn_insv): Likewise.

gcc/testsuite/ChangeLog:

	* gcc.target/aarch64/cond_op-1.c: New test.
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pinskia committed Oct 22, 2023
1 parent c9ae68f commit bcc5054
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47 changes: 47 additions & 0 deletions gcc/config/aarch64/aarch64.md
Original file line number Diff line number Diff line change
Expand Up @@ -4413,6 +4413,53 @@
[(set_attr "type" "csel")]
)

;; There are two canonical forms for `cmp ? ~a : a`.
;; This is the second form and is here to help combine.
;; Support `-(cmp) ^ a` into `cmp ? ~a : a`
;; The second pattern is to support the zero extend'ed version.

(define_insn_and_split "*cmov<mode>_insn_insv"
[(set (match_operand:GPI 0 "register_operand" "=r")
(xor:GPI
(neg:GPI
(match_operator:GPI 1 "aarch64_comparison_operator"
[(match_operand 2 "cc_register" "") (const_int 0)]))
(match_operand:GPI 3 "general_operand" "r")))]
""
"#"
"&& true"
[(set (match_dup 0)
(if_then_else:GPI (match_dup 1)
(not:GPI (match_dup 3))
(match_dup 3)))]
{
/* After reload this will be a nop due to the constraint. */
operands[3] = force_reg (<MODE>mode, operands[3]);
}
[(set_attr "type" "csel")]
)

(define_insn_and_split "*cmov_uxtw_insn_insv"
[(set (match_operand:DI 0 "register_operand" "=r")
(zero_extend:DI
(xor:SI
(neg:SI
(match_operator:SI 1 "aarch64_comparison_operator"
[(match_operand 2 "cc_register" "") (const_int 0)]))
(match_operand:SI 3 "general_operand" "r"))))]
"can_create_pseudo_p ()"
"#"
"&& true"
[(set (match_dup 0)
(if_then_else:DI (match_dup 1)
(zero_extend:DI (not:SI (match_dup 3)))
(zero_extend:DI (match_dup 3))))]
{
operands[3] = force_reg (SImode, operands[3]);
}
[(set_attr "type" "csel")]
)

;; If X can be loaded by a single CNT[BHWD] instruction,
;;
;; A = UMAX (B, X)
Expand Down
20 changes: 20 additions & 0 deletions gcc/testsuite/gcc.target/aarch64/cond_op-1.c
Original file line number Diff line number Diff line change
@@ -0,0 +1,20 @@
/* { dg-do compile } */
/* { dg-options "-O2" } */
/* PR target/110986 */


long long full(unsigned a, unsigned b)
{
return a ? ~b : b;
}
unsigned fuu(unsigned a, unsigned b)
{
return a ? ~b : b;
}
long long fllll(unsigned long long a, unsigned long long b)
{
return a ? ~b : b;
}

/* { dg-final { scan-assembler-times "csinv\tw\[0-9\]*" 2 } } */
/* { dg-final { scan-assembler-times "csinv\tx\[0-9\]*" 1 } } */

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