[PATCH] [Aarch64] Variable shift count truncation issues

[Andreas Schwab]

On Jun 23 2017, Michael Collison <Michael.Collison@arm.com> wrote:

> diff --git a/gcc/testsuite/gcc.target/aarch64/var_shift_mask_1.c b/gcc/testsuite/gcc.target/aarch64/var_shift_mask_1.c
> new file mode 100644
> index 0000000..e2b020e
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/aarch64/var_shift_mask_1.c
> @@ -0,0 +1,61 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2" } */
> +
> +/* The integer variable shift and rotate instructions truncate their
> +   shift amounts by the datasize.  Make sure that we don't emit a redundant
> +   masking operation.  */
> +
> +unsigned
> +f1 (unsigned x, int y)
> +{
> +  return x << (y & 31);
> +}
> +
> +unsigned long
> +f2 (unsigned long x, int y)
> +{
> +  return x << (y & 63);
> +}
> +
> +unsigned long
> +f3 (unsigned long bit_addr, int y)
> +{
> +  unsigned long bitnumb = bit_addr & 63;
> +  return (1L << bitnumb);
> +}
> +
> +unsigned int
> +f4 (unsigned int x, unsigned int y)
> +{
> +  y &= 31;
> +  return x >> y | (x << (32 - y));
> +}
> +
> +unsigned long
> +f5 (unsigned long x, unsigned long y)
> +{
> +  y &= 63;
> +  return x >> y | (x << (64 - y));
> +}
> +
> +unsigned long
> +f6 (unsigned long x, unsigned long y)
> +{
> +
> +  return (x << (64 - (y & 63)));
> +
> +}
> +
> +unsigned long
> +f7 (unsigned long x, unsigned long y)
> +{
> +  return (x << -(y & 63));
> +}
> +
> +/* { dg-final { scan-assembler-times "lsl\tw\[0-9\]+, w\[0-9\]+, w\[0-9\]+" 1 } } */
> +/* { dg-final { scan-assembler-times "lsl\tx\[0-9\]+, x\[0-9\]+, x\[0-9\]+" 4 } } */
> +/* { dg-final { scan-assembler-times "ror\tw\[0-9\]+, w\[0-9\]+, w\[0-9\]+" 1 } } */
> +/* { dg-final { scan-assembler-times "ror\tx\[0-9\]+, x\[0-9\]+, x\[0-9\]+" 1 } } */
> +/* { dg-final { scan-assembler-not "and\tw\[0-9\]+, w\[0-9\]+, 31" } } */
> +/* { dg-final { scan-assembler-not "and\tx\[0-9\]+, x\[0-9\]+, 63" } } */
> +/* { dg-final { scan-assembler-not "sub\tw\[0-9\]+, w\[0-9\]+, w\[0-9\]+" } } */

That fails with -mabi=ilp32.

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."