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[PATCH] simplify-rtx: Remove non-simplifying simplification (PR77729)
- From: Segher Boessenkool <segher at kernel dot crashing dot org>
- To: gcc-patches at gcc dot gnu dot org
- Cc: Segher Boessenkool <segher at kernel dot crashing dot org>
- Date: Mon, 2 Oct 2017 19:35:46 +0000
- Subject: [PATCH] simplify-rtx: Remove non-simplifying simplification (PR77729)
- Authentication-results: sourceware.org; auth=none
If we have (X&C1)|C2 simplify_binary_operation_1 makes C1 as small as
possible. This makes worse code in common cases like when the AND with
C1 is from a zero-extension. This patch fixes it by removing this
transformation (twice).
I tested this on 31 targets, also some variations that do the
transformation only for some conditions (like, do not do it if the
resulting constant looks "worse", e.g. has more stretches of ones).
22 of those targets show no difference; 8 are best with this patch
variant (never do the transformation); and 64-bit hppa is not best,
but the difference is only four insns in a million.
Bootstrapped and tested on powerpc64-linux {-m32,-m64}. Is this okay
for trunk? And backports?
Segher
2017-10-02 Segher Boessenkool <segher@kernel.crashing.org>
PR rtl-optimization/77729
* simplify-rtx.c (simplify_binary_operation_1): Delete the (X&C1)|C2
to (X&(C1&~C2))|C2 transformations.
---
gcc/simplify-rtx.c | 25 -------------------------
1 file changed, 25 deletions(-)
diff --git a/gcc/simplify-rtx.c b/gcc/simplify-rtx.c
index 1b960b9..3b6cf6f 100644
--- a/gcc/simplify-rtx.c
+++ b/gcc/simplify-rtx.c
@@ -2673,14 +2673,6 @@ simplify_binary_operation_1 (enum rtx_code code, machine_mode mode,
/* If (C1|C2) == ~0 then (X&C1)|C2 becomes X|C2. */
if (((c1|c2) & mask) == mask)
return simplify_gen_binary (IOR, mode, XEXP (op0, 0), op1);
-
- /* Minimize the number of bits set in C1, i.e. C1 := C1 & ~C2. */
- if (((c1 & ~c2) & mask) != (c1 & mask))
- {
- tem = simplify_gen_binary (AND, mode, XEXP (op0, 0),
- gen_int_mode (c1 & ~c2, mode));
- return simplify_gen_binary (IOR, mode, tem, op1);
- }
}
/* Convert (A & B) | A to A. */
@@ -2736,23 +2728,6 @@ simplify_binary_operation_1 (enum rtx_code code, machine_mode mode,
return gen_rtx_ROTATE (int_mode, XEXP (opright, 0),
XEXP (SUBREG_REG (opleft), 1));
- /* If we have (ior (and (X C1) C2)), simplify this by making
- C1 as small as possible if C1 actually changes. */
- if (CONST_INT_P (op1)
- && (HWI_COMPUTABLE_MODE_P (mode)
- || INTVAL (op1) > 0)
- && GET_CODE (op0) == AND
- && CONST_INT_P (XEXP (op0, 1))
- && CONST_INT_P (op1)
- && (UINTVAL (XEXP (op0, 1)) & UINTVAL (op1)) != 0)
- {
- rtx tmp = simplify_gen_binary (AND, mode, XEXP (op0, 0),
- gen_int_mode (UINTVAL (XEXP (op0, 1))
- & ~UINTVAL (op1),
- mode));
- return simplify_gen_binary (IOR, mode, tmp, op1);
- }
-
/* If OP0 is (ashiftrt (plus ...) C), it might actually be
a (sign_extend (plus ...)). Then check if OP1 is a CONST_INT and
the PLUS does not affect any of the bits in OP1: then we can do
--
1.8.3.1