[llvm] f0df421 - [X86] Add a simple hack to IsProfitableToFold to prevent vselect+strict fp operations from being folded into masked instructions.

[Craig Topper via llvm-commits]

Author: Craig Topper
Date: 2019-12-18T14:42:56-08:00
New Revision: f0df4218b67d0abe96867804b8932b9b88998f51

URL: https://github.com/llvm/llvm-project/commit/f0df4218b67d0abe96867804b8932b9b88998f51
DIFF: https://github.com/llvm/llvm-project/commit/f0df4218b67d0abe96867804b8932b9b88998f51.diff

LOG: [X86] Add a simple hack to IsProfitableToFold to prevent vselect+strict fp operations from being folded into masked instructions.

We really need to update the isel patterns to prevent this, but
that requires some tablegen de-tangling. So this hack will work
for correctness in the short term.

Added: 
    

Modified: 
    llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
    llvm/test/CodeGen/X86/vector-constrained-fp-intrinsics.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp b/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
index d60e08c409cb..592e64842070 100644
--- a/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
+++ b/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
@@ -580,6 +580,12 @@ X86DAGToDAGISel::IsProfitableToFold(SDValue N, SDNode *U, SDNode *Root) const {
   if (!N.hasOneUse())
     return false;
 
+  // FIXME: Temporary hack to prevent strict floating point nodes from
+  // folding into masked operations illegally.
+  if (U == Root && Root->getOpcode() == ISD::VSELECT &&
+      N.getOpcode() != ISD::LOAD && N.getOpcode() != X86ISD::VBROADCAST_LOAD)
+    return false;
+
   if (N.getOpcode() != ISD::LOAD)
     return true;
 

diff  --git a/llvm/test/CodeGen/X86/vector-constrained-fp-intrinsics.ll b/llvm/test/CodeGen/X86/vector-constrained-fp-intrinsics.ll
index 82c798ab170b..27bc9c13d4d8 100644
--- a/llvm/test/CodeGen/X86/vector-constrained-fp-intrinsics.ll
+++ b/llvm/test/CodeGen/X86/vector-constrained-fp-intrinsics.ll
@@ -7317,7 +7317,8 @@ define <16 x float> @vpaddd_mask_test(<16 x float> %i, <16 x float> %j, <16 x i3
 ; AVX512-LABEL: vpaddd_mask_test:
 ; AVX512:       # %bb.0:
 ; AVX512-NEXT:    vptestmd %zmm2, %zmm2, %k1
-; AVX512-NEXT:    vaddps %zmm1, %zmm0, %zmm0 {%k1}
+; AVX512-NEXT:    vaddps %zmm1, %zmm0, %zmm1
+; AVX512-NEXT:    vmovaps %zmm1, %zmm0 {%k1}
 ; AVX512-NEXT:    retq
   %mask = icmp ne <16 x i32> %mask1, zeroinitializer
   %x = call <16 x float> @llvm.experimental.constrained.fadd.v16f32(<16 x float> %i, <16 x float> %j, metadata !"round.dynamic", metadata !"fpexcept.strict") #0