mirror/gcc
1
0
Fork 0
mirror of https://github.com/gcc-mirror/gcc.git synced 2024-11-21 13:40:47 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

simplify-rtx: Optimize (x - 1) * y + y [PR98334]

Browse Source 
We don't try to optimize for signed x, y (int) (x - 1U) * y + y
into x * y, we can't do that with signed x * y, because the former
is well defined for INT_MIN and -1, while the latter is not.
We could perhaps optimize it during isel or some very late optimization
where we'd turn magically flag_wrapv, but we don't do that yet.

This patch optimizes it in simplify-rtx.c, such that we can optimize
it during combine.

2021-01-05  Jakub Jelinek  <jakub@redhat.com>

	PR rtl-optimization/98334
	* simplify-rtx.c (simplify_context::simplify_binary_operation_1):
	Optimize (X - 1) * Y + Y to X * Y or (X + 1) * Y - Y to X * Y.

	* gcc.target/i386/pr98334.c: New test.
This commit is contained in:
Jakub Jelinek 2021-01-05 10:57:52 +01:00
parent 6b69738c1e
commit 4615cde5d7
2 changed files with 92 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

56
gcc/simplify-rtx.c
View File

@ -2602,6 +2602,42 @@ simplify_context::simplify_binary_operation_1 (rtx_code code,
return (set_src_cost (tem, int_mode, speed)
<= set_src_cost (orig, int_mode, speed) ? tem : 0);
}
/* Optimize (X - 1) * Y + Y to X * Y. */
lhs = op0;
rhs = op1;
if (GET_CODE (op0) == MULT)
{
if (((GET_CODE (XEXP (op0, 0)) == PLUS
&& XEXP (XEXP (op0, 0), 1) == constm1_rtx)
|| (GET_CODE (XEXP (op0, 0)) == MINUS
&& XEXP (XEXP (op0, 0), 1) == const1_rtx))
&& rtx_equal_p (XEXP (op0, 1), op1))
lhs = XEXP (XEXP (op0, 0), 0);
else if (((GET_CODE (XEXP (op0, 1)) == PLUS
&& XEXP (XEXP (op0, 1), 1) == constm1_rtx)
|| (GET_CODE (XEXP (op0, 1)) == MINUS
&& XEXP (XEXP (op0, 1), 1) == const1_rtx))
&& rtx_equal_p (XEXP (op0, 0), op1))
lhs = XEXP (XEXP (op0, 1), 0);
}
else if (GET_CODE (op1) == MULT)
{
if (((GET_CODE (XEXP (op1, 0)) == PLUS
&& XEXP (XEXP (op1, 0), 1) == constm1_rtx)
|| (GET_CODE (XEXP (op1, 0)) == MINUS
&& XEXP (XEXP (op1, 0), 1) == const1_rtx))
&& rtx_equal_p (XEXP (op1, 1), op0))
rhs = XEXP (XEXP (op1, 0), 0);
else if (((GET_CODE (XEXP (op1, 1)) == PLUS
&& XEXP (XEXP (op1, 1), 1) == constm1_rtx)
|| (GET_CODE (XEXP (op1, 1)) == MINUS
&& XEXP (XEXP (op1, 1), 1) == const1_rtx))
&& rtx_equal_p (XEXP (op1, 0), op0))
rhs = XEXP (XEXP (op1, 1), 0);
}
if (lhs != op0 || rhs != op1)
return simplify_gen_binary (MULT, int_mode, lhs, rhs);
}
/* (plus (xor X C1) C2) is (xor X (C1^C2)) if C2 is signbit. */
@ -2789,6 +2825,26 @@ simplify_context::simplify_binary_operation_1 (rtx_code code,
return (set_src_cost (tem, int_mode, speed)
<= set_src_cost (orig, int_mode, speed) ? tem : 0);
}
/* Optimize (X + 1) * Y - Y to X * Y. */
lhs = op0;
if (GET_CODE (op0) == MULT)
{
if (((GET_CODE (XEXP (op0, 0)) == PLUS
&& XEXP (XEXP (op0, 0), 1) == const1_rtx)
|| (GET_CODE (XEXP (op0, 0)) == MINUS
&& XEXP (XEXP (op0, 0), 1) == constm1_rtx))
&& rtx_equal_p (XEXP (op0, 1), op1))
lhs = XEXP (XEXP (op0, 0), 0);
else if (((GET_CODE (XEXP (op0, 1)) == PLUS
&& XEXP (XEXP (op0, 1), 1) == const1_rtx)
|| (GET_CODE (XEXP (op0, 1)) == MINUS
&& XEXP (XEXP (op0, 1), 1) == constm1_rtx))
&& rtx_equal_p (XEXP (op0, 0), op1))
lhs = XEXP (XEXP (op0, 1), 0);
}
if (lhs != op0)
return simplify_gen_binary (MULT, int_mode, lhs, op1);
}
/* (a - (-b)) -> (a + b). True even for IEEE. */

36
gcc/testsuite/gcc.target/i386/pr98334.c Normal file
View File

@ -0,0 +1,36 @@
/* PR rtl-optimization/98334 */
/* { dg-do compile } */
/* { dg-options "-O2 -fomit-frame-pointer -fno-stack-protector" } */
/* { dg-final { scan-assembler-not "\taddl\t" } } */
/* { dg-final { scan-assembler-not "\tsubl\t" } } */
/* { dg-final { scan-assembler-not "\tleal\t" } } */
int
foo (int i, unsigned int n)
{
int result = 0;
while (n > 0)
{
result += i;
n -= 1;
}
return result;
}
int
bar (int x, int y)
{
return (int) (y - 1U) * x + x;
}
int
baz (int x, int y)
{
return (y - 1) * x + x;
}
int
qux (int x, int y)
{
return x * (int) (y + 1U) - x;
}