diff mbox series

[committed] Avoid right shifting signed value on ext-dce.cc

Message ID 6e77d7b5-cc28-4e13-bb1a-54c64bed297e@gmail.com
State New
Headers show
Series [committed] Avoid right shifting signed value on ext-dce.cc | expand

Commit Message

Jeff Law Aug. 17, 2024, 9:13 p.m. UTC 
This is analogous to a prior patch to ext-dce which fixes propagation of 
sign bits, but this time for the saturating variants.  I'd held off 
fixing those because I wanted the time to look at that code (since we 
don't have a testcase for it as far as I know).

Not surprisingly, putting an abort on that path and running an x86 
bootstrap and testsuite run, it never triggers.  Of course not a lot of 
code tries to do saturating shifts.

Anyway, bootstrapped and regression tested on x86_64.  Pushing to the trunk.

Thanks for everyone's patience.

Jeff
commit 61e179b1b363454926504fac13b554ad7f1b0f72
Author: Jeff Law <jlaw@ventanamicro.com>
Date:   Sat Aug 17 15:10:38 2024 -0600

    [committed] Avoid right shifting signed value on ext-dce.cc
    
    This is analogous to a prior patch to ext-dce which fixes propagation of sign
    bits, but this time for the saturating variants.  I'd held off fixing those
    because I wanted the time to look at that code (since we don't have a testcase
    for it as far as I know).
    
    Not surprisingly, putting an abort on that path and running an x86 bootstrap
    and testsuite run, it never triggers.  Of course not a lot of code tries to do
    saturating shifts.
    
    Anyway, bootstrapped and regression tested on x86_64.  Pushing to the trunk.
    
    Thanks for everyone's patience.
    
    gcc/
            * ext-dce.cc (carry_backpropagate): Cast mask to HOST_WIDE_INT before
            shifting.
diff mbox series

Patch

diff --git a/gcc/ext-dce.cc b/gcc/ext-dce.cc
index 97a66427118..017e2de000d 100644
--- a/gcc/ext-dce.cc
+++ b/gcc/ext-dce.cc
@@ -556,7 +556,7 @@  carry_backpropagate (unsigned HOST_WIDE_INT mask, enum rtx_code code, rtx x)
 			     >> (INTVAL (XEXP (x, 1))
 				 + (XEXP (x, 1) != const0_rtx
 				    && code == SS_ASHIFT))))
-		  | (mask >> INTVAL (XEXP (x, 1))));
+		  | ((HOST_WIDE_INT)mask >> INTVAL (XEXP (x, 1))));
 	}
       return mmask;