Never attempt to join an early-clobber def with a regular kill.

This fixes PR14194.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@166880 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/RegisterCoalescer.cpp

@@ -1492,6 +1492,20 @@ JoinVals::analyzeValue(unsigned ValNo, JoinVals &Other) {
   if ((V.WriteLanes & OtherV.ValidLanes) == 0)
     return CR_Replace;
 
+  // If the other live range is killed by DefMI and the live ranges are still
+  // overlapping, it must be because we're looking at an early clobber def:
+  //
+  //   %dst<def,early-clobber> = ASM %src<kill>
+  //
+  // In this case, it is illegal to merge the two live ranges since the early
+  // clobber def would clobber %src before it was read.
+  if (OtherLRQ.isKill()) {
+    // This case where the def doesn't overlap the kill is handled above.
+    assert(VNI->def.isEarlyClobber() &&
+           "Only early clobber defs can overlap a kill");
+    return CR_Impossible;
+  }
+
   // VNI is clobbering live lanes in OtherVNI, but there is still the
   // possibility that no instructions actually read the clobbered lanes.
   // If we're clobbering all the lanes in OtherVNI, at least one must be read.

test/CodeGen/X86/crash.ll

@@ -580,3 +580,12 @@ bb28:                                             ; preds = %bb21
 bb29:                                             ; preds = %bb28, %bb26, %bb25, %bb21
   unreachable
 }
+
+define void @pr14194() nounwind uwtable {
+  %tmp = load i64* undef, align 16
+  %tmp1 = trunc i64 %tmp to i32
+  %tmp2 = lshr i64 %tmp, 32
+  %tmp3 = trunc i64 %tmp2 to i32
+  %tmp4 = call { i32, i32 } asm sideeffect "", "=&r,=&r,r,r,0,1,~{dirflag},~{fpsr},~{flags}"(i32 %tmp3, i32 undef, i32 %tmp3, i32 %tmp1) nounwind
+ ret void
+}