[RDF] Handle undefined registers in RDF copy propagation

When updating the graph, make sure that new uses without reaching defs
are handled correctly.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267891 91177308-0d34-0410-b5e6-96231b3b80d8

Author: Krzysztof Parzyszek

lib/Target/Hexagon/RDFCopy.cpp

@@ -218,7 +218,12 @@ bool CopyPropagation::run() {
         Op.setReg(SR.Reg);
         Op.setSubReg(SR.Sub);
         DFG.unlinkUse(UA, false);
-        UA.Addr->linkToDef(UA.Id, DFG.addr<DefNode*>(RDefSR_SA));
+        if (RDefSR_SA != 0) {
+          UA.Addr->linkToDef(UA.Id, DFG.addr<DefNode*>(RDefSR_SA));
+        } else {
+          UA.Addr->setReachingDef(0);
+          UA.Addr->setSibling(0);
+        }
 
         Changed = true;
   #ifndef NDEBUG

test/CodeGen/Hexagon/rdf-copy-undef2.ll

@@ -0,0 +1,55 @@
+; RUN: llc -march=hexagon < %s
+; REQUIRES: asserts
+
+target triple = "hexagon"
+
+declare void @llvm.lifetime.start(i64, i8* nocapture) #0
+declare void @llvm.lifetime.end(i64, i8* nocapture) #0
+declare signext i16 @cat(i16 signext) #1
+declare void @danny(i16 signext, i16 signext, i16 signext, i16* nocapture readonly, i16 signext, i16* nocapture) #1
+declare void @sammy(i16* nocapture readonly, i16* nocapture readonly, i16* nocapture readonly, i32* nocapture, i16* nocapture, i16 signext, i16 signext, i16 signext) #1
+declare i8* @llvm.stacksave() #2
+declare void @llvm.stackrestore(i8*) #2
+
+define i32 @fred(i16 signext %p0, i16 signext %p1, i16* nocapture readonly %p2, i16 signext %p3, i16* nocapture readonly %p4, i16* nocapture %p5) #1 {
+entry:
+  %0 = tail call i8* @llvm.stacksave()
+  %vla = alloca i16, i32 undef, align 8
+  %call17 = call signext i16 @cat(i16 signext 1) #1
+  br i1 undef, label %for.cond23.preheader, label %for.end47
+
+for.cond23.preheader:                             ; preds = %for.end40, %entry
+  %i.190 = phi i16 [ %inc46, %for.end40 ], [ 0, %entry ]
+  br i1 undef, label %for.body27, label %for.end40
+
+for.body27:                                       ; preds = %for.body27, %for.cond23.preheader
+  %indvars.iv = phi i32 [ %indvars.iv.next, %for.body27 ], [ 0, %for.cond23.preheader ]
+  %call30 = call signext i16 @cat(i16 signext 7) #1
+  %arrayidx32 = getelementptr inbounds i16, i16* %vla, i32 %indvars.iv
+  store i16 %call30, i16* %arrayidx32, align 2
+  %arrayidx37 = getelementptr inbounds i16, i16* undef, i32 %indvars.iv
+  %indvars.iv.next = add nuw nsw i32 %indvars.iv, 1
+  %exitcond = icmp eq i16 undef, %p3
+  br i1 %exitcond, label %for.end40, label %for.body27
+
+for.end40:                                        ; preds = %for.body27, %for.cond23.preheader
+  call void @sammy(i16* nonnull undef, i16* undef, i16* %p4, i32* null, i16* undef, i16 signext undef, i16 signext undef, i16 signext undef) #1
+  %inc46 = add nuw nsw i16 %i.190, 1
+  %exitcond94 = icmp eq i16 %inc46, %call17
+  br i1 %exitcond94, label %for.end47.loopexit, label %for.cond23.preheader
+
+for.end47.loopexit:                               ; preds = %for.end40
+  %.pre = load i16, i16* undef, align 2
+  br label %for.end47
+
+for.end47:                                        ; preds = %for.end47.loopexit, %entry
+  %1 = phi i16 [ %.pre, %for.end47.loopexit ], [ 0, %entry ]
+  call void @danny(i16 signext %1, i16 signext %p0, i16 signext %p1, i16* %p2, i16 signext %p3, i16* %p5) #1
+  call void @llvm.stackrestore(i8* %0)
+  ret i32 undef
+}
+
+
+attributes #0 = { argmemonly nounwind }
+attributes #1 = { optsize }
+attributes #2 = { nounwind }