[RS6000] ICE in decompose, at rtl.h:2282

[Alan Modra via Gcc-patches]

during RTL pass: fwprop1
gcc.dg/pr82596.c: In function 'test_cststring':
gcc.dg/pr82596.c:27:1: internal compiler error: in decompose, at rtl.h:2282

-m32 gcc/testsuite/gcc.dg/pr82596.c fails along with other tests after
applying rtx_cost patches, which exposed a backend bug.

legitimize_address when presented with the following address
        (plus (reg) (const_int 0x7ffffffff))
attempts to rewrite it as a high/low sum.  The low part is 0xffff, or
-1, making the high part 0x80000000.  But this is no longer canonical
for SImode.

Bootstrapped and regression tested powerpc64-linux biarch and
powerpc64le-linux.  OK?

        * config/rs6000/rs6000.c (rs6000_legitimize_address): Properly
        sign extend high part of address constant.

diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index 375fff59928..d0924d59a65 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -8364,7 +8364,7 @@ rs6000_legitimize_address (rtx x, rtx oldx 
ATTRIBUTE_UNUSED,
        low_int = 0;
       high_int = INTVAL (XEXP (x, 1)) - low_int;
       sum = force_operand (gen_rtx_PLUS (Pmode, XEXP (x, 0),
-                                        GEN_INT (high_int)), 0);
+                                        gen_int_mode (high_int, Pmode)), 0);
       return plus_constant (Pmode, sum, low_int);
     }
   else if (GET_CODE (x) == PLUS

-- 
Alan Modra
Australia Development Lab, IBM