Add DAG-combines for aggressive FMA formation.

This patch adds DAG combines to form FMAs from pairs of FADD + FMUL or
FSUB + FMUL. The combines are performed when:
(a) Either
      AllowExcessFPPrecision option (-enable-excess-fp-precision for llc)
        OR
      UnsafeFPMath option (-enable-unsafe-fp-math)
    are set, and
(b) TargetLoweringInfo::isFMAFasterThanMulAndAdd(VT) is true for the type of
    the FADD/FSUB, and
(c) The FMUL only has one user (the FADD/FSUB).

If your target has fast FMA instructions you can make use of these combines by
overriding TargetLoweringInfo::isFMAFasterThanMulAndAdd(VT) to return true for
types supported by your FMA instruction, and adding patterns to match ISD::FMA
to your FMA instructions.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@158757 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 3 insertions, 3 deletions

diff --git a/tools/llc/llc.cpp b/tools/llc/llc.cpp
index d0880913ba..b303cec3b5 100644
--- a/tools/llc/llc.cpp
+++ b/tools/llc/llc.cpp
@@ -156,8 +156,8 @@ DisableFPElimNonLeaf("disable-non-leaf-fp-elim",
   cl::init(false));
 
 static cl::opt<bool>
-DisableExcessPrecision("disable-excess-fp-precision",
-  cl::desc("Disable optimizations that may increase FP precision"),
+EnableExcessPrecision("enable-excess-fp-precision",
+  cl::desc("Enable optimizations that may increase FP precision"),
   cl::init(false));
 
 static cl::opt<bool>
@@ -404,7 +404,7 @@ int main(int argc, char **argv) {
   Options.LessPreciseFPMADOption = EnableFPMAD;
   Options.NoFramePointerElim = DisableFPElim;
   Options.NoFramePointerElimNonLeaf = DisableFPElimNonLeaf;
-  Options.NoExcessFPPrecision = DisableExcessPrecision;
+  Options.AllowExcessFPPrecision = EnableExcessPrecision;
   Options.UnsafeFPMath = EnableUnsafeFPMath;
   Options.NoInfsFPMath = EnableNoInfsFPMath;
   Options.NoNaNsFPMath = EnableNoNaNsFPMath;