[AVX-512] Make VEX encoded FMA instructions available when AVX512 is enabled regardless of whether +fma was added on the command line.

We weren't able to handle isel of the 128/256-bit FMA instructions when AVX512F was enabled but VLX and FMA weren't.

I didn't mask FeatureAVX512 imply FeatureFMA as I wasn't sure I wanted disabling FMA to also disable AVX512. Instead we just can't prevent FMA instructions if AVX512 is enabled.

Another option would be to promote 128/256-bit to 512-bit, do the operation and extract it. But that requires a lot of extra isel patterns. Since no CPUs exist that support AVX512, but not FMA just using the VEX instructions seems better.

llvm-svn: 298051

1 files changed, 2 insertions, 2 deletions

diff --git a/llvm/lib/Target/X86/X86Subtarget.h b/llvm/lib/Target/X86/X86Subtarget.h
index 3f4cd7d0b1d..c2c95658482 100644
--- a/llvm/lib/Target/X86/X86Subtarget.h
+++ b/llvm/lib/Target/X86/X86Subtarget.h
@@ -435,9 +435,9 @@ public:
   bool hasPCLMUL() const { return HasPCLMUL; }
   // Prefer FMA4 to FMA - its better for commutation/memory folding and
   // has equal or better performance on all supported targets.
-  bool hasFMA() const { return HasFMA && !HasFMA4; }
+  bool hasFMA() const { return (HasFMA || hasAVX512()) && !HasFMA4; }
   bool hasFMA4() const { return HasFMA4; }
-  bool hasAnyFMA() const { return hasFMA() || hasFMA4() || hasAVX512(); }
+  bool hasAnyFMA() const { return hasFMA() || hasFMA4(); }
   bool hasXOP() const { return HasXOP; }
   bool hasTBM() const { return HasTBM; }
   bool hasMOVBE() const { return HasMOVBE; }