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[PATCH][ARM] Adjust arith_shiftsi for ARMv8-style

Hi all,

Shifted arithmetic operations can never be encoded in 16-bits in and therefore can not appear in Thumb2 IT blocks under ARMv8-A rules (and the -mrestrict-it rules). This patch adjusts the relevant pattern for that purpose.

Tested and bootstrapped on arm-none-linux-gnueabihf and made sure no performance regressions on a number of benchmarks.

This is a bug (not wrong-code though) in -mrestrict-it that affects 4.9 as well as trunk, so is it ok to backport it there?


2014-05-15  Kyrylo Tkachov  <>

    * config/arm/ (arith_shiftsi): Do not predicate for
commit 8d54d43e84925ee5c53e70ecc7036bc5a7e867ba
Author: Kyrylo Tkachov <>
Date:   Fri Apr 4 16:10:39 2014 +0100

    [ARM] Adjust arith_shiftsi for arm_restrict_it

diff --git a/gcc/config/arm/ b/gcc/config/arm/
index 38ca058..9468c70 100644
--- a/gcc/config/arm/
+++ b/gcc/config/arm/
@@ -9860,6 +9860,7 @@
   "%i1%?\\t%0, %2, %4%S3"
   [(set_attr "predicable" "yes")
+   (set_attr "predicable_short_it" "no")
    (set_attr "shift" "4")
    (set_attr "arch" "a,t2,t2,a")
    ;; Thumb2 doesn't allow the stack pointer to be used for 

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