This patch fixes the regression caused by the changes to add square root
estimation when compiling for xgene-1 or exynos-m1 targets.
The issue is that the expand path for the reciprocal estimate square
root pattern assumes that pattern cannot fail once it has been decided
that this expansion path is available, but because the logic deep inside
aarch64_emit_approx_sqrt() differs from use_rsqrt_p() the two disagree
as to what is safe.
This patch refactors the logic to ensure that we cannot unknowingly make
different choices here.
Bootstrap/testing completed ok. I'll apply this to trunk.
Jakub: Are we having an RC2? If so, is this ok for the gcc-7 branch?
PR target/80530
* config/aarch64/aarch64.c (aarch64_emit_approx_sqrt): Ensure
that the logic for permitting reciprocal estimates matches that
in use_rsqrt_p.
R.
diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index 1e58e9d..6ef49da 100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -7971,33 +7971,40 @@ aarch64_emit_approx_sqrt (rtx dst, rtx src, bool recp)
machine_mode mode = GET_MODE (dst);
if (GET_MODE_INNER (mode) == HFmode)
- return false;
+ {
+ gcc_assert (!recp);
+ return false;
+ }
- machine_mode mmsk = mode_for_vector
- (int_mode_for_mode (GET_MODE_INNER (mode)),
- GET_MODE_NUNITS (mode));
- bool use_approx_sqrt_p = (!recp
- && (flag_mlow_precision_sqrt
- || (aarch64_tune_params.approx_modes->sqrt
- & AARCH64_APPROX_MODE (mode))));
- bool use_approx_rsqrt_p = (recp
- && (flag_mrecip_low_precision_sqrt
- ||
(aarch64_tune_params.approx_modes->recip_sqrt
- & AARCH64_APPROX_MODE (mode))));
+ machine_mode mmsk
+ = mode_for_vector (int_mode_for_mode (GET_MODE_INNER (mode)),
+ GET_MODE_NUNITS (mode));
+ if (!recp)
+ {
+ if (!(flag_mlow_precision_sqrt
+ || (aarch64_tune_params.approx_modes->sqrt
+ & AARCH64_APPROX_MODE (mode))))
+ return false;
+
+ if (flag_finite_math_only
+ || flag_trapping_math
+ || !flag_unsafe_math_optimizations
+ || optimize_function_for_size_p (cfun))
+ return false;
+ }
+ else
+ /* Caller assumes we cannot fail. */
+ gcc_assert (use_rsqrt_p (mode));
- if (!flag_finite_math_only
- || flag_trapping_math
- || !flag_unsafe_math_optimizations
- || !(use_approx_sqrt_p || use_approx_rsqrt_p)
- || optimize_function_for_size_p (cfun))
- return false;
rtx xmsk = gen_reg_rtx (mmsk);
if (!recp)
- /* When calculating the approximate square root, compare the argument with
- 0.0 and create a mask. */
- emit_insn (gen_rtx_SET (xmsk, gen_rtx_NEG (mmsk, gen_rtx_EQ (mmsk, src,
- CONST0_RTX (mode)))));
+ /* When calculating the approximate square root, compare the
+ argument with 0.0 and create a mask. */
+ emit_insn (gen_rtx_SET (xmsk,
+ gen_rtx_NEG (mmsk,
+ gen_rtx_EQ (mmsk, src,
+ CONST0_RTX (mode)))));
/* Estimate the approximate reciprocal square root. */
rtx xdst = gen_reg_rtx (mode);
