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tcg/optimize: Fix sign_mask for logical right-shift

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The 'sign' computation is attempting to locate the sign bit that has
been repeated, so that we can test if that bit is known zero.  That
computation can be zero if there are no known sign repetitions.

Cc: qemu-stable@nongnu.org
Fixes: 93a967fbb5 ("tcg/optimize: Propagate sign info for shifting")
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2248
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
This commit is contained in:
Richard Henderson
2024-03-26 11:21:38 -10:00
parent 889cd5a8e2
commit 2911e9b95f
3 changed files with 30 additions and 1 deletions
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2
tcg/optimize.c
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@ -2376,7 +2376,7 @@ static bool fold_shift(OptContext *ctx, TCGOp *op)
* will not reduced the number of input sign repetitions.
*/
sign = (s_mask & -s_mask) >> 1;
if (!(z_mask & sign)) {
if (sign && !(z_mask & sign)) {
ctx->s_mask = s_mask;
}
break;