From: Sanjay Patel <spatel@rotateright.com>
Date: Fri, 5 Sep 2014 22:26:22 +0000 (+0000)
Subject: Allow vector fsub ops with constants to get the same optimizations as scalars.
X-Git-Url: http://plrg.eecs.uci.edu/git/?p=oota-llvm.git;a=commitdiff_plain;h=52af82df95e656434b89638bbd095cd4252b880e

Allow vector fsub ops with constants to get the same optimizations as scalars.

This problem is bigger than just fsub, but this is the minimum fix to solve
fneg for PR20556 ( http://llvm.org/bugs/show_bug.cgi?id=20556 ), and we solve
zero subtraction with the same change.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@217286 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 5d95af69fab..a465cdb9725 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -6754,8 +6754,8 @@ SDValue DAGCombiner::visitFADD(SDNode *N) {
 SDValue DAGCombiner::visitFSUB(SDNode *N) {
   SDValue N0 = N->getOperand(0);
   SDValue N1 = N->getOperand(1);
-  ConstantFPSDNode *N0CFP = dyn_cast<ConstantFPSDNode>(N0);
-  ConstantFPSDNode *N1CFP = dyn_cast<ConstantFPSDNode>(N1);
+  ConstantFPSDNode *N0CFP = isConstOrConstSplatFP(N0);
+  ConstantFPSDNode *N1CFP = isConstOrConstSplatFP(N1);
   EVT VT = N->getValueType(0);
   SDLoc dl(N);
   const TargetOptions &Options = DAG.getTarget().Options;
diff --git a/test/CodeGen/X86/vec_unsafe-fp-math.ll b/test/CodeGen/X86/vec_unsafe-fp-math.ll
new file mode 100644
index 00000000000..827d4184d11
--- /dev/null
+++ b/test/CodeGen/X86/vec_unsafe-fp-math.ll
@@ -0,0 +1,23 @@
+; RUN: llc < %s -enable-unsafe-fp-math -mtriple=x86_64-unknown-unknown -mcpu=corei7 | FileCheck %s
+
+; Make sure that vectors get the same benefits as scalars when using unsafe-fp-math.
+
+; Subtracting zero is free.
+define <4 x float> @vec_fsub_zero(<4 x float> %x) {
+; CHECK-LABEL: vec_fsub_zero:
+; CHECK-NOT: subps
+; CHECK-NOT: xorps
+; CHECK: retq
+  %sub = fsub <4 x float> %x, zeroinitializer
+  ret <4 x float> %sub
+}
+
+; Negating doesn't require subtraction.
+define <4 x float> @vec_fneg(<4 x float> %x) {
+; CHECK-LABEL: vec_fneg:
+; CHECK: xorps  {{.*}}LCP{{.*}}, %xmm0
+; CHECK-NOT: subps
+; CHECK-NEXT: retq
+  %sub = fsub <4 x float> zeroinitializer, %x
+  ret <4 x float> %sub
+}