As per Joseph's suggestion here:
http://gcc.gnu.org/ml/gcc-patches/2011-05/msg00846.html
I am re-posting machine-independent parts of my ARM fixed-point support
patches, with explanations as to why each part is necessary.
This is the first: on ARM, TARGET_LIB_INT_CMP_BIASED is false for
TARGET_BPABI targets (i.e. most currently-interesting cases --
EABI comparison helper functions return -1/0/1 for lt/eq/gt rather than
0/1/2). However the fixed-point helper library uses biased comparisons
unconditionally. So, this patch just makes comparisons between
fixed-point quantities use the biasing rather than not. (Grepping
config/, in practice, this will only affect ARM.)
Tested in a series with other fixed-point patches. OK to apply?
Julian
ChangeLog
gcc/
* optabs.c (prepare_cmp_insn): Use correct biasing for fixed-point
comparison helpers.
commit 12efebd5f56358c2d194659570ad05e089bbaaf3
Author: Julian Brown <[email protected]>
Date: Fri May 13 05:42:15 2011 -0700
Correct biasing for fixed-point optabs.
diff --git a/gcc/optabs.c b/gcc/optabs.c
index 62e123b..a1b85b8 100644
--- a/gcc/optabs.c
+++ b/gcc/optabs.c
@@ -3930,11 +3930,13 @@ prepare_cmp_insn (rtx x, rtx y, enum rtx_code comparison, rtx size,
result against 1 in the biased case, and zero in the unbiased
case. For unsigned comparisons always compare against 1 after
biasing the unbiased result by adding 1. This gives us a way to
- represent LTU. */
+ represent LTU.
+ The comparisons in the fixed-point helper library are always
+ biased. */
x = result;
y = const1_rtx;
- if (!TARGET_LIB_INT_CMP_BIASED)
+ if (!TARGET_LIB_INT_CMP_BIASED && !ALL_FIXED_POINT_MODE_P (mode))
{
if (unsignedp)
x = plus_constant (result, 1);
