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
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 @@
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 @@
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 @@
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);