[PATCH] rs6000: Properly handle LE index munging in vec_shr (PR94710)

[Segher Boessenkool]

The PR shows the compiler crashing with -mvsx -mlittle -O0.  This turns
out to be caused by a failure to make of the higher bits in an index
endian conversion.

Tested on powerpc64-linux {-m32,-m64} and on powerpc64le-linux.

Committing to trunk.

(This will need backports).


Segher


2020-04-24  Segher Boessenkool  <seg...@kernel.crashing.org>

        PR target/94710
        * config/rs6000/vector.md (vec_shr_<mode> for VEC_L): Correct little
        endian byteshift_val calculation.
---
 gcc/config/rs6000/vector.md | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/gcc/config/rs6000/vector.md b/gcc/config/rs6000/vector.md
index 5bc8f80..662521e 100644
--- a/gcc/config/rs6000/vector.md
+++ b/gcc/config/rs6000/vector.md
@@ -1426,7 +1426,8 @@ (define_expand "vec_shr_<mode>"
   emit_move_insn (zero_reg, CONST0_RTX (<MODE>mode));
   if (!BYTES_BIG_ENDIAN)
     {
-      byteshift_val = 16 - byteshift_val;
+      /* Note, byteshift_val can be 0!  */
+      byteshift_val = -byteshift_val & 15;
       op1 = zero_reg;
       op2 = operands[1];
     }
-- 
1.8.3.1