From 8a9d0572be18bd1ee8faec64a1628f5bb33096a5 Mon Sep 17 00:00:00 2001 From: rth Date: Thu, 11 Nov 2010 18:42:35 +0000 Subject: [PATCH] * tree-ssa-math-opts.c (convert_mult_to_fma): Do not verify that the target has the exact fma operation that we matched. git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@166611 138bc75d-0d04-0410-961f-82ee72b054a4 --- gcc/ChangeLog | 5 +++++ 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 + + * 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 * 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) -- 2.7.4