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| author | Julian Brown <julian@codesourcery.com> | 2020-11-30 11:10:04 -0800 |
|---|---|---|
| committer | Julian Brown <julian@codesourcery.com> | 2021-01-12 16:46:01 -0800 |
| commit | c8812bac8ee39f73ea881e4f6260acf5590b4190 (patch) | |
| tree | 705063c5b9410785f858502398a8516c6bc78630 /gcc/config/gcn/gcn.md | |
| parent | abb3993e49c04bd40e42f196f55785cc3fd81682 (diff) | |
| download | gcc-c8812bac8ee39f73ea881e4f6260acf5590b4190.zip gcc-c8812bac8ee39f73ea881e4f6260acf5590b4190.tar.gz gcc-c8812bac8ee39f73ea881e4f6260acf5590b4190.tar.bz2 | |
amdgcn: Improve FP division accuracy
GCN has a reciprocal-approximation instruction but no
hardware divide. This patch adjusts the open-coded reciprocal
approximation/Newton-Raphson refinement steps to use fused multiply-add
instructions as is necessary to obtain a properly-rounded result, and
adds further refinement steps to correctly round the full division result.
The patterns in question are still guarded by a flag_reciprocal_math
condition, and do not yet support denormals.
2021-01-13 Julian Brown <julian@codesourcery.com>
gcc/
* config/gcn/gcn-valu.md (recip<mode>2<exec>, recip<mode>2): Use unspec
for reciprocal-approximation instructions.
(div<mode>3): Use fused multiply-accumulate operations for reciprocal
refinement and division result.
* config/gcn/gcn.md (UNSPEC_RCP): New unspec constant.
gcc/testsuite/
* gcc.target/gcn/fpdiv.c: New test.
Diffstat (limited to 'gcc/config/gcn/gcn.md')
| -rw-r--r-- | gcc/config/gcn/gcn.md | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/gcc/config/gcn/gcn.md b/gcc/config/gcn/gcn.md index 757e575..b5f895a 100644 --- a/gcc/config/gcn/gcn.md +++ b/gcc/config/gcn/gcn.md @@ -80,7 +80,8 @@ UNSPEC_MOV_DPP_SHR UNSPEC_MOV_FROM_LANE63 UNSPEC_GATHER - UNSPEC_SCATTER]) + UNSPEC_SCATTER + UNSPEC_RCP]) ;; }}} ;; {{{ Attributes |