From: Jeff Law <jlaw@ventanamicro.com>
Date: Wed, 5 Feb 2025 21:22:33 +0000 (-0700)
Subject: [committed] Disable ABS instruction on bfin port
X-Git-Tag: basepoints/gcc-16~2172
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=3e08a4ecea27c54fda90e8f58641b1986ad957e1;p=thirdparty%2Fgcc.git

[committed] Disable ABS instruction on bfin port

I was looking at a regression on the bfin port with a recent change to the IRA
and stumbled across this just doing a general port healthyness evaluation.

The ABS instruction in the blackfin ISA is defined as saturating on INT_MIN,
which is a bit unexpected.  We certainly can't use it when -fwrapv is enabled.
Given the failures on the C23 uabs tests, I'm inclined to just disable the
pattern completely.

Fixes pr23047, uabs-2 and uabs-3.

While it's not a regression, it's the blackfin port, so I think we've got a
higher degree of freedom here.

Pushing to the trunk.

gcc/
	* config/bfin/bfin.md (abssi): Disable pattern.
---

diff --git a/gcc/config/bfin/bfin.md b/gcc/config/bfin/bfin.md
index 810bd52cadf0..27c156b6c1e8 100644
--- a/gcc/config/bfin/bfin.md
+++ b/gcc/config/bfin/bfin.md
@@ -1440,12 +1440,15 @@
   "%0 = min(%1,%2)%!"
   [(set_attr "type" "dsp32")])
 
-(define_insn "abssi2"
-  [(set (match_operand:SI 0 "register_operand" "=d")
-	(abs:SI (match_operand:SI 1 "register_operand" "d")))]
-  ""
-  "%0 = abs %1%!"
-  [(set_attr "type" "dsp32")])
+;; The ABS instruction is defined as saturating.  So at the least
+;; it is inappropriate for -fwrapv.  This also fixes the C23 uabs
+;; tests.
+;;(define_insn "abssi2"
+;;  [(set (match_operand:SI 0 "register_operand" "=d")
+;;	(abs:SI (match_operand:SI 1 "register_operand" "d")))]
+;;  ""
+;;  "%0 = abs %1%!"
+;;  [(set_attr "type" "dsp32")])
 
 (define_insn "ssabssi2"
   [(set (match_operand:SI 0 "register_operand" "=d")