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| author | Richard Henderson <rth@redhat.com> | 2010-11-11 10:42:35 -0800 |
|---|---|---|
| committer | Richard Henderson <rth@gcc.gnu.org> | 2010-11-11 10:42:35 -0800 |
| commit | a1d8aa4b1fc433931788b63d51e652969509e4cd (patch) | |
| tree | ef82f67ce81c13bd9e9d05a3fa9df5b50b2da485 /gcc | |
| parent | 658bd5ca00275d0a7b1a987018bc663b8a2d4a57 (diff) | |
| download | gcc-a1d8aa4b1fc433931788b63d51e652969509e4cd.zip gcc-a1d8aa4b1fc433931788b63d51e652969509e4cd.tar.gz gcc-a1d8aa4b1fc433931788b63d51e652969509e4cd.tar.bz2 | |
tree-ssa-math-opts.c (convert_mult_to_fma): Do not verify that the target has the exact fma operation that we matched.
* tree-ssa-math-opts.c (convert_mult_to_fma): Do not verify
that the target has the exact fma operation that we matched.
From-SVN: r166611
Diffstat (limited to 'gcc')
| -rw-r--r-- | gcc/ChangeLog | 5 | ||||
| -rw-r--r-- | gcc/tree-ssa-math-opts.c | 26 |
2 files changed, 17 insertions, 14 deletions
diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 542d959..2cdcaf2 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,8 @@ +2010-11-11 Richard Henderson <rth@redhat.com> + + * tree-ssa-math-opts.c (convert_mult_to_fma): Do not verify + that the target has the exact fma operation that we matched. + 2010-11-11 Joseph Myers <joseph@codesourcery.com> * reginfo.c (fix_register): Avoid inserting English word in diff --git a/gcc/tree-ssa-math-opts.c b/gcc/tree-ssa-math-opts.c index 2840150..a2dfac6 100644 --- a/gcc/tree-ssa-math-opts.c +++ b/gcc/tree-ssa-math-opts.c @@ -1531,7 +1531,6 @@ convert_mult_to_fma (gimple mul_stmt) enum tree_code use_code; tree result = mul_result; bool negate_p = false; - optab opt; use_stmt = USE_STMT (use_p); @@ -1574,32 +1573,31 @@ convert_mult_to_fma (gimple mul_stmt) negate_p = true; } - /* Determine if the target supports the exact form we found. */ switch (use_code) { case MINUS_EXPR: - if (gimple_assign_rhs1 (use_stmt) == result) - { - opt = negate_p ? fnms_optab : fms_optab; - break; - } - negate_p = !negate_p; - /* FALLTHRU */ - + if (gimple_assign_rhs2 (use_stmt) == result) + negate_p = !negate_p; + break; case PLUS_EXPR: - opt = negate_p ? fnma_optab : fma_optab; break; - default: /* FMA can only be formed from PLUS and MINUS. */ return false; } - if (optab_handler (opt, TYPE_MODE (type)) == CODE_FOR_nothing) - return false; /* We can't handle a * b + a * b. */ if (gimple_assign_rhs1 (use_stmt) == gimple_assign_rhs2 (use_stmt)) return false; + + /* While it is possible to validate whether or not the exact form + that we've recognized is available in the backend, the assumption + is that the transformation is never a loss. For instance, suppose + the target only has the plain FMA pattern available. Consider + a*b-c -> fma(a,b,-c): we've exchanged MUL+SUB for FMA+NEG, which + is still two operations. Consider -(a*b)-c -> fma(-a,b,-c): we + still have 3 operations, but in the FMA form the two NEGs are + independant and could be run in parallel. */ } FOR_EACH_IMM_USE_STMT (use_stmt, imm_iter, mul_result) |