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, 1 insertions, 1 deletions

diff --git a/lib/Target/ARM/ARMInstrInfo.td b/lib/Target/ARM/ARMInstrInfo.td
index 5131152d1e..81e3527a6f 100644
--- a/lib/Target/ARM/ARMInstrInfo.td
+++ b/lib/Target/ARM/ARMInstrInfo.td
@@ -236,7 +236,7 @@ def UseFPVMLx        : Predicate<"Subtarget->useFPVMLx()">;
 // Prefer fused MAC for fp mul + add over fp VMLA / VMLS if they are available.
 // But only select them if more precision in FP computation is allowed.
 // Do not use them for Darwin platforms.
-def UseFusedMAC      : Predicate<"!TM.Options.NoExcessFPPrecision && "
+def UseFusedMAC      : Predicate<"TM.Options.AllowExcessFPPrecision && "
                                  "!Subtarget->isTargetDarwin()">;
 def DontUseFusedMAC  : Predicate<"!Subtarget->hasVFP4() || "
                                  "Subtarget->isTargetDarwin()">;