| Message ID | 20130409122433.lbfstq22o0g4g4ko-nzlynne@webmail.spamcop.net |
|---|---|
| State | New |
| Headers | show |
On Tue, Apr 9, 2013 at 6:24 PM, Joern Rennecke <joern.rennecke@embecosm.com> wrote: > Quoting Richard Biener <richard.guenther@gmail.com>: > >> I don't see that. It's merely a complication of optimal handling of >> a * b +- c * d vs. just a * b +- c. The pass does simple pattern matching >> only, not doing a global optimal transform, so adding another special-case >> is reasonable. Special-casing just for single-use 2nd multiplication >> simplifies the cases for example. > > > I have attached a version of the patch that uses this simpler test. > Currently bootstrapping / regtesting on i686-pc-linux-gnu . Ok if the testing succeeds. Thanks, Richard. > > gcc: > 2013-04-09 Joern Rennecke <joern.rennecke@embecosm.com> > > PR tree-optimization/55524 > * tree-ssa-math-opts.c > (convert_mult_to_fma): Don't use an fms construct > when we don't have an fms operation, but fnma, and it looks > likely that we'll be able to use the latter. > > gcc/testsuite: > 2013-04-09 Joern Rennecke <joern.rennecke@embecosm.com> > > PR tree-optimization/55524 > * gcc.target/epiphany/fnma-1.c: New test. > > Index: testsuite/gcc.target/epiphany/fnma-1.c > =================================================================== > --- testsuite/gcc.target/epiphany/fnma-1.c (revision 0) > +++ testsuite/gcc.target/epiphany/fnma-1.c (working copy) > @@ -0,0 +1,9 @@ > +/* { dg-do compile } */ > +/* { dg-options "-O2" } */ > +/* { dg-final { scan-assembler-times "fmsub\[ \ta-zA-Z0-9\]*," 1 } } */ > + > +float > +f (float ar, float ai, float br, float bi) > +{ > + return ar * br - ai * bi; > +} > Index: tree-ssa-math-opts.c > =================================================================== > --- tree-ssa-math-opts.c (revision 197578) > +++ tree-ssa-math-opts.c (working copy) > @@ -2570,6 +2570,24 @@ convert_mult_to_fma (gimple mul_stmt, tr > return false; > } > > + /* If the subtrahend (gimple_assign_rhs2 (use_stmt)) is computed > + by a MULT_EXPR that we'll visit later, we might be able to > + get a more profitable match with fnma. > + OTOH, if we don't, a negate / fma pair has likely lower latency > + that a mult / subtract pair. */ > + if (use_code == MINUS_EXPR && !negate_p > + && gimple_assign_rhs1 (use_stmt) == result > + && optab_handler (fms_optab, TYPE_MODE (type)) == CODE_FOR_nothing > + && optab_handler (fnma_optab, TYPE_MODE (type)) != > CODE_FOR_nothing) > + { > + tree rhs2 = gimple_assign_rhs2 (use_stmt); > + gimple stmt2 = SSA_NAME_DEF_STMT (rhs2); > + > + if (has_single_use (rhs2) > + && gimple_assign_rhs_code (stmt2) == MULT_EXPR) > + return false; > + } > + > /* We can't handle a * b + a * b. */ > if (gimple_assign_rhs1 (use_stmt) == gimple_assign_rhs2 (use_stmt)) > return false; >
Index: testsuite/gcc.target/epiphany/fnma-1.c =================================================================== --- testsuite/gcc.target/epiphany/fnma-1.c (revision 0) +++ testsuite/gcc.target/epiphany/fnma-1.c (working copy) @@ -0,0 +1,9 @@ +/* { dg-do compile } */ +/* { dg-options "-O2" } */ +/* { dg-final { scan-assembler-times "fmsub\[ \ta-zA-Z0-9\]*," 1 } } */ + +float +f (float ar, float ai, float br, float bi) +{ + return ar * br - ai * bi; +} Index: tree-ssa-math-opts.c =================================================================== --- tree-ssa-math-opts.c (revision 197578) +++ tree-ssa-math-opts.c (working copy) @@ -2570,6 +2570,24 @@ convert_mult_to_fma (gimple mul_stmt, tr return false; } + /* If the subtrahend (gimple_assign_rhs2 (use_stmt)) is computed + by a MULT_EXPR that we'll visit later, we might be able to + get a more profitable match with fnma. + OTOH, if we don't, a negate / fma pair has likely lower latency + that a mult / subtract pair. */ + if (use_code == MINUS_EXPR && !negate_p + && gimple_assign_rhs1 (use_stmt) == result + && optab_handler (fms_optab, TYPE_MODE (type)) == CODE_FOR_nothing + && optab_handler (fnma_optab, TYPE_MODE (type)) != CODE_FOR_nothing) + { + tree rhs2 = gimple_assign_rhs2 (use_stmt); + gimple stmt2 = SSA_NAME_DEF_STMT (rhs2); + + if (has_single_use (rhs2) + && gimple_assign_rhs_code (stmt2) == MULT_EXPR) + return false; + } + /* We can't handle a * b + a * b. */ if (gimple_assign_rhs1 (use_stmt) == gimple_assign_rhs2 (use_stmt)) return false;