When unsafe math is used, we can use commutative FMAX and FMIN. In some cases

this allows for better code generation.

Added a new DAGCombine transformation to convert FMAX and FMIN to FMANC and
FMINC, which are commutative.

For example:

  movaps  %xmm0, %xmm1
  movsd LC(%rip), %xmm0
  minsd %xmm1, %xmm0

becomes:

  minsd LC(%rip), %xmm0




git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@162187 91177308-0d34-0410-b5e6-96231b3b80d8

4 files changed, 59 insertions, 3 deletions

diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index e59ab80..e4af736 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -11463,6 +11463,8 @@ const char *X86TargetLowering::getTargetNodeName(unsigned Opcode) const {
   case X86ISD::FHSUB:              return "X86ISD::FHSUB";
   case X86ISD::FMAX:               return "X86ISD::FMAX";
   case X86ISD::FMIN:               return "X86ISD::FMIN";
+  case X86ISD::FMAXC:              return "X86ISD::FMAXC";
+  case X86ISD::FMINC:              return "X86ISD::FMINC";
   case X86ISD::FRSQRT:             return "X86ISD::FRSQRT";
   case X86ISD::FRCP:               return "X86ISD::FRCP";
   case X86ISD::TLSADDR:            return "X86ISD::TLSADDR";
@@ -15368,6 +15370,29 @@ static SDValue PerformFORCombine(SDNode *N, SelectionDAG &DAG) {
   return SDValue();
 }
 
+/// PerformFMinFMaxCombine - Do target-specific dag combines on X86ISD::FMIN and
+/// X86ISD::FMAX nodes.
+static SDValue PerformFMinFMaxCombine(SDNode *N, SelectionDAG &DAG) {
+  assert(N->getOpcode() == X86ISD::FMIN || N->getOpcode() == X86ISD::FMAX);
+
+  // Only perform optimizations if UnsafeMath is used.
+  if (!DAG.getTarget().Options.UnsafeFPMath)
+    return SDValue();
+
+  // If we run in unsafe-math mode, then convert the FMAX and FMIN nodes
+  // into FMINC and MMAXC, which are Commutative operations.
+  unsigned NewOp = 0;
+  switch (N->getOpcode()) {
+    default: llvm_unreachable("unknown opcode");
+    case X86ISD::FMIN:  NewOp = X86ISD::FMINC; break;
+    case X86ISD::FMAX:  NewOp = X86ISD::FMAXC; break;
+  }
+
+  return DAG.getNode(NewOp, N->getDebugLoc(), N->getValueType(0),
+                     N->getOperand(0), N->getOperand(1));
+}
+
+
 /// PerformFANDCombine - Do target-specific dag combines on X86ISD::FAND nodes.
 static SDValue PerformFANDCombine(SDNode *N, SelectionDAG &DAG) {
   // FAND(0.0, x) -> 0.0
@@ -15849,6 +15874,8 @@ SDValue X86TargetLowering::PerformDAGCombine(SDNode *N,
   case ISD::FSUB:           return PerformFSUBCombine(N, DAG, Subtarget);
   case X86ISD::FXOR:
   case X86ISD::FOR:         return PerformFORCombine(N, DAG);
+  case X86ISD::FMIN:
+  case X86ISD::FMAX:        return PerformFMinFMaxCombine(N, DAG);
   case X86ISD::FAND:        return PerformFANDCombine(N, DAG);
   case X86ISD::BT:          return PerformBTCombine(N, DAG, DCI);
   case X86ISD::VZEXT_MOVL:  return PerformVZEXT_MOVLCombine(N, DAG);
diff --git a/lib/Target/X86/X86ISelLowering.h b/lib/Target/X86/X86ISelLowering.h
index 896d067..74f5167 100644
--- a/lib/Target/X86/X86ISelLowering.h
+++ b/lib/Target/X86/X86ISelLowering.h
@@ -195,6 +195,9 @@ namespace llvm {
       ///
       FMAX, FMIN,
 
+      /// FMAXC, FMINC - Commutative FMIN and FMAX.
+      FMAXC, FMINC,
+
       /// FRSQRT, FRCP - Floating point reciprocal-sqrt and reciprocal
       /// approximation.  Note that these typically require refinement
       /// in order to obtain suitable precision.
diff --git a/lib/Target/X86/X86InstrFragmentsSIMD.td b/lib/Target/X86/X86InstrFragmentsSIMD.td
index 1db68c8..ee2d3c4 100644
--- a/lib/Target/X86/X86InstrFragmentsSIMD.td
+++ b/lib/Target/X86/X86InstrFragmentsSIMD.td
@@ -29,6 +29,13 @@ def SDTX86VFCMP : SDTypeProfile<1, 3, [SDTCisInt<0>, SDTCisSameAs<1, 2>,
 
 def X86fmin    : SDNode<"X86ISD::FMIN",      SDTFPBinOp>;
 def X86fmax    : SDNode<"X86ISD::FMAX",      SDTFPBinOp>;
+
+// Commutative and Associative FMIN and FMAX.
+def X86fminc    : SDNode<"X86ISD::FMINC", SDTFPBinOp,
+    [SDNPCommutative, SDNPAssociative]>;
+def X86fmaxc    : SDNode<"X86ISD::FMAXC", SDTFPBinOp,
+    [SDNPCommutative, SDNPAssociative]>;
+
 def X86fand    : SDNode<"X86ISD::FAND",      SDTFPBinOp,
                         [SDNPCommutative, SDNPAssociative]>;
 def X86for     : SDNode<"X86ISD::FOR",       SDTFPBinOp,
@@ -73,11 +80,12 @@ def X86vzmovl  : SDNode<"X86ISD::VZEXT_MOVL",
                  SDTypeProfile<1, 1, [SDTCisSameAs<0,1>]>>;
 
 def X86vzmovly  : SDNode<"X86ISD::VZEXT_MOVL",
-                 SDTypeProfile<1, 1, [SDTCisVec<0>, SDTCisVec<1>, 
+                 SDTypeProfile<1, 1, [SDTCisVec<0>, SDTCisVec<1>,
                                       SDTCisOpSmallerThanOp<1, 0> ]>>;
 
 def X86vsmovl  : SDNode<"X86ISD::VSEXT_MOVL",
-                 SDTypeProfile<1, 1, [SDTCisVec<0>, SDTCisInt<1>, SDTCisInt<0>]>>;
+                 SDTypeProfile<1, 1,
+                 [SDTCisVec<0>, SDTCisInt<1>, SDTCisInt<0>]>>;
 
 def X86vzload  : SDNode<"X86ISD::VZEXT_LOAD", SDTLoad,
                         [SDNPHasChain, SDNPMayLoad, SDNPMemOperand]>;
diff --git a/lib/Target/X86/X86InstrSSE.td b/lib/Target/X86/X86InstrSSE.td
index 20dc81e..220c06d 100644
--- a/lib/Target/X86/X86InstrSSE.td
+++ b/lib/Target/X86/X86InstrSSE.td
@@ -2872,7 +2872,8 @@ let isCommutable = 0 in {
               basic_sse12_fp_binop_s_int<0x5C, "sub", SSE_ALU_ITINS_S, 0>,
                 VEX_4V, VEX_LIG;
   defm VSUB : basic_sse12_fp_binop_p<0x5C, "sub", fsub, SSE_ALU_ITINS_P, 0>,
-              basic_sse12_fp_binop_p_y<0x5C, "sub", fsub, SSE_ALU_ITINS_P>, VEX_4V;
+              basic_sse12_fp_binop_p_y<0x5C, "sub", fsub, SSE_ALU_ITINS_P>,
+                VEX_4V;
   defm VDIV : basic_sse12_fp_binop_s<0x5E, "div", fdiv, SSE_DIV_ITINS_S, 0>,
               basic_sse12_fp_binop_s_int<0x5E, "div", SSE_DIV_ITINS_S, 0>,
                 VEX_4V, VEX_LIG;
@@ -2923,6 +2924,23 @@ let Constraints = "$src1 = $dst" in {
   }
 }
 
+let isCommutable = 1, isCodeGenOnly = 1 in {
+  defm VMAXC: basic_sse12_fp_binop_s<0x5F, "max", X86fmaxc, SSE_ALU_ITINS_S, 0>,
+       VEX_4V, VEX_LIG;
+  defm VMAXC: basic_sse12_fp_binop_p<0x5F, "max", X86fmaxc, SSE_ALU_ITINS_P, 0>,
+       basic_sse12_fp_binop_p_y<0x5F, "max", X86fmaxc, SSE_ALU_ITINS_P>, VEX_4V;
+  defm VMINC: basic_sse12_fp_binop_s<0x5D, "min", X86fminc, SSE_ALU_ITINS_S, 0>,
+       VEX_4V, VEX_LIG;
+  defm VMINC: basic_sse12_fp_binop_p<0x5D, "min", X86fminc, SSE_ALU_ITINS_P, 0>,
+       basic_sse12_fp_binop_p_y<0x5D, "min", X86fminc, SSE_ALU_ITINS_P>, VEX_4V;
+  let Constraints = "$src1 = $dst" in {
+    defm MAXC: basic_sse12_fp_binop_s<0x5F, "max", X86fmaxc, SSE_ALU_ITINS_S>,
+         basic_sse12_fp_binop_p<0x5F, "max", X86fmaxc, SSE_ALU_ITINS_P>;
+    defm MINC: basic_sse12_fp_binop_s<0x5D, "min", X86fminc, SSE_ALU_ITINS_S>,
+         basic_sse12_fp_binop_p<0x5D, "min", X86fminc, SSE_ALU_ITINS_P>;
+  }
+}
+
 /// Unop Arithmetic
 /// In addition, we also have a special variant of the scalar form here to
 /// represent the associated intrinsic operation.  This form is unlike the