From cd5bbd8bad58562dff9979bbba73b840443fe9e5 Mon Sep 17 00:00:00 2001
From: Ahmed Bougacha <ahmed.bougacha@gmail.com>
Date: Mon, 12 Jan 2015 20:31:30 +0000
Subject: [PATCH] [X86] Also create+widen FMIN/FMAX nodes for v2f32.

This happens in the HINT benchmark, where the SLP-vectorizer created
v2f32 fcmp/select code.  The "correct" solution would have been to
teach the vectorizer cost model that v2f32 isn't legal (because really,
it isn't), but if we can vectorize we might as well do so.

We legalize these v2f32 FMIN/FMAX nodes by widening to v4f32 later on.
v3f32 were already widened to v4f32 by the generic unroll-and-build-vector
legalization.

rdar://15763436
Differential Revision: http://reviews.llvm.org/D6557


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225691 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/X86/X86ISelLowering.cpp | 19 +++++++++++++++-
 test/CodeGen/X86/sse-minmax.ll     | 36 ++++++++++++++++++++++++++++++
 2 files changed, 54 insertions(+), 1 deletion(-)

diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 65440a0d22a..f455700d5ad 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -19658,6 +19658,22 @@ void X86TargetLowering::ReplaceNodeResults(SDNode *N,
   switch (N->getOpcode()) {
   default:
     llvm_unreachable("Do not know how to custom type legalize this operation!");
+  // We might have generated v2f32 FMIN/FMAX operations. Widen them to v4f32.
+  case X86ISD::FMINC:
+  case X86ISD::FMIN:
+  case X86ISD::FMAXC:
+  case X86ISD::FMAX: {
+    EVT VT = N->getValueType(0);
+    if (VT != MVT::v2f32)
+      llvm_unreachable("Unexpected type (!= v2f32) on FMIN/FMAX.");
+    SDValue UNDEF = DAG.getUNDEF(VT);
+    SDValue LHS = DAG.getNode(ISD::CONCAT_VECTORS, dl, MVT::v4f32,
+                              N->getOperand(0), UNDEF);
+    SDValue RHS = DAG.getNode(ISD::CONCAT_VECTORS, dl, MVT::v4f32,
+                              N->getOperand(1), UNDEF);
+    Results.push_back(DAG.getNode(N->getOpcode(), dl, MVT::v4f32, LHS, RHS));
+    return;
+  }
   case ISD::SIGN_EXTEND_INREG:
   case ISD::ADDC:
   case ISD::ADDE:
@@ -23077,8 +23093,9 @@ static SDValue PerformSELECTCombine(SDNode *N, SelectionDAG &DAG,
   // instructions match the semantics of the common C idiom x<y?x:y but not
   // x<=y?x:y, because of how they handle negative zero (which can be
   // ignored in unsafe-math mode).
+  // We also try to create v2f32 min/max nodes, which we later widen to v4f32.
   if (Cond.getOpcode() == ISD::SETCC && VT.isFloatingPoint() &&
-      VT != MVT::f80 && TLI.isTypeLegal(VT) &&
+      VT != MVT::f80 && (TLI.isTypeLegal(VT) || VT == MVT::v2f32) &&
       (Subtarget->hasSSE2() ||
        (Subtarget->hasSSE1() && VT.getScalarType() == MVT::f32))) {
     ISD::CondCode CC = cast<CondCodeSDNode>(Cond.getOperand(2))->get();
diff --git a/test/CodeGen/X86/sse-minmax.ll b/test/CodeGen/X86/sse-minmax.ll
index 46f2b56dd93..4dcb54ca4b0 100644
--- a/test/CodeGen/X86/sse-minmax.ll
+++ b/test/CodeGen/X86/sse-minmax.ll
@@ -989,3 +989,39 @@ define <4 x float> @test_minps(<4 x float> %x, <4 x float> %y) nounwind {
   %min = select <4 x i1> %min_is_x, <4 x float> %x, <4 x float> %y
   ret <4 x float> %min
 }
+
+; UNSAFE-LABEL: test_maxps_illegal_v2f32:
+; UNSAFE-NEXT: maxps %xmm1, %xmm0
+; UNSAFE-NEXT: ret
+define <2 x float> @test_maxps_illegal_v2f32(<2 x float> %x, <2 x float> %y) nounwind {
+  %max_is_x = fcmp oge <2 x float> %x, %y
+  %max = select <2 x i1> %max_is_x, <2 x float> %x, <2 x float> %y
+  ret <2 x float> %max
+}
+
+; UNSAFE-LABEL: test_minps_illegal_v2f32:
+; UNSAFE-NEXT: minps %xmm1, %xmm0
+; UNSAFE-NEXT: ret
+define <2 x float> @test_minps_illegal_v2f32(<2 x float> %x, <2 x float> %y) nounwind {
+  %min_is_x = fcmp ole <2 x float> %x, %y
+  %min = select <2 x i1> %min_is_x, <2 x float> %x, <2 x float> %y
+  ret <2 x float> %min
+}
+
+; UNSAFE-LABEL: test_maxps_illegal_v3f32:
+; UNSAFE-NEXT: maxps %xmm1, %xmm0
+; UNSAFE-NEXT: ret
+define <3 x float> @test_maxps_illegal_v3f32(<3 x float> %x, <3 x float> %y) nounwind {
+  %max_is_x = fcmp oge <3 x float> %x, %y
+  %max = select <3 x i1> %max_is_x, <3 x float> %x, <3 x float> %y
+  ret <3 x float> %max
+}
+
+; UNSAFE-LABEL: test_minps_illegal_v3f32:
+; UNSAFE-NEXT: minps %xmm1, %xmm0
+; UNSAFE-NEXT: ret
+define <3 x float> @test_minps_illegal_v3f32(<3 x float> %x, <3 x float> %y) nounwind {
+  %min_is_x = fcmp ole <3 x float> %x, %y
+  %min = select <3 x i1> %min_is_x, <3 x float> %x, <3 x float> %y
+  ret <3 x float> %min
+}
-- 
2.34.1