From e87cadc49a9f6e327d09add0b2ab81d9c062cdc8 Mon Sep 17 00:00:00 2001
From: Tim Northover <tnorthover@apple.com>
Date: Sat, 10 May 2014 07:37:50 +0000
Subject: [PATCH] ARM64: fix SELECT_CC lowering in absence of NaNs.

We were swapping the true & false results while testing for FMAX/FMIN,
but not putting them back to the original state if the later checks
failed.

Should fix PR19700.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@208469 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/ARM64/ARM64ISelLowering.cpp | 17 +++++++++--------
 test/CodeGen/ARM64/fmax.ll             | 17 +++++++++++++++--
 2 files changed, 24 insertions(+), 10 deletions(-)

diff --git a/lib/Target/ARM64/ARM64ISelLowering.cpp b/lib/Target/ARM64/ARM64ISelLowering.cpp
index bff6ba060fb..b422ddcb43d 100644
--- a/lib/Target/ARM64/ARM64ISelLowering.cpp
+++ b/lib/Target/ARM64/ARM64ISelLowering.cpp
@@ -3121,17 +3121,18 @@ SDValue ARM64TargetLowering::LowerSELECT_CC(SDValue Op,
 
   // Try to match this select into a max/min operation, which have dedicated
   // opcode in the instruction set.
-  // NOTE: This is not correct in the presence of NaNs, so we only enable this
+  // FIXME: This is not correct in the presence of NaNs, so we only enable this
   // in no-NaNs mode.
   if (getTargetMachine().Options.NoNaNsFPMath) {
-    if (selectCCOpsAreFMaxCompatible(LHS, FVal) &&
-        selectCCOpsAreFMaxCompatible(RHS, TVal)) {
+    SDValue MinMaxLHS = TVal, MinMaxRHS = FVal;
+    if (selectCCOpsAreFMaxCompatible(LHS, MinMaxRHS) &&
+        selectCCOpsAreFMaxCompatible(RHS, MinMaxLHS)) {
       CC = ISD::getSetCCSwappedOperands(CC);
-      std::swap(TVal, FVal);
+      std::swap(MinMaxLHS, MinMaxRHS);
     }
 
-    if (selectCCOpsAreFMaxCompatible(LHS, TVal) &&
-        selectCCOpsAreFMaxCompatible(RHS, FVal)) {
+    if (selectCCOpsAreFMaxCompatible(LHS, MinMaxLHS) &&
+        selectCCOpsAreFMaxCompatible(RHS, MinMaxRHS)) {
       switch (CC) {
       default:
         break;
@@ -3141,7 +3142,7 @@ SDValue ARM64TargetLowering::LowerSELECT_CC(SDValue Op,
       case ISD::SETUGE:
       case ISD::SETOGT:
       case ISD::SETOGE:
-        return DAG.getNode(ARM64ISD::FMAX, dl, VT, TVal, FVal);
+        return DAG.getNode(ARM64ISD::FMAX, dl, VT, MinMaxLHS, MinMaxRHS);
         break;
       case ISD::SETLT:
       case ISD::SETLE:
@@ -3149,7 +3150,7 @@ SDValue ARM64TargetLowering::LowerSELECT_CC(SDValue Op,
       case ISD::SETULE:
       case ISD::SETOLT:
       case ISD::SETOLE:
-        return DAG.getNode(ARM64ISD::FMIN, dl, VT, TVal, FVal);
+        return DAG.getNode(ARM64ISD::FMIN, dl, VT, MinMaxLHS, MinMaxRHS);
         break;
       }
     }
diff --git a/test/CodeGen/ARM64/fmax.ll b/test/CodeGen/ARM64/fmax.ll
index 53ecf86a022..94b745437bd 100644
--- a/test/CodeGen/ARM64/fmax.ll
+++ b/test/CodeGen/ARM64/fmax.ll
@@ -1,7 +1,7 @@
 ; RUN: llc -march=arm64 -enable-no-nans-fp-math < %s | FileCheck %s
 
 define double @test_direct(float %in) #1 {
-entry:
+; CHECK-LABEL: test_direct:
   %cmp = fcmp olt float %in, 0.000000e+00
   %longer = fpext float %in to double
   %val = select i1 %cmp, double 0.000000e+00, double %longer
@@ -11,7 +11,7 @@ entry:
 }
 
 define double @test_cross(float %in) #1 {
-entry:
+; CHECK-LABEL: test_cross:
   %cmp = fcmp olt float %in, 0.000000e+00
   %longer = fpext float %in to double
   %val = select i1 %cmp, double %longer, double 0.000000e+00
@@ -19,3 +19,16 @@ entry:
 
 ; CHECK: fmin
 }
+
+; This isn't a min or a max, but passes the first condition for swapping the
+; results. Make sure they're put back before we resort to the normal fcsel.
+define float @test_cross_fail(float %lhs, float %rhs) {
+; CHECK-LABEL: test_cross_fail:
+  %tst = fcmp une float %lhs, %rhs
+  %res = select i1 %tst, float %rhs, float %lhs
+  ret float %res
+
+  ; The register allocator would have to decide to be deliberately obtuse before
+  ; other register were used.
+; CHECK: fcsel s0, s1, s0, ne
+}
\ No newline at end of file
-- 
2.34.1