File backport-llvm-r197909 of Package llvm

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r197909 | rsandifo | 2013-12-23 15:51:56 +0100 (Mon, 23 Dec 2013) | 8 lines

Fix Scalarizer insertion point when replacing PHIs with insertelements

If the Scalarizer scalarized a vector PHI but could not scalarize
all uses of it, it would insert a series of insertelements to reconstruct
the vector PHI value from the scalar ones.  The problem was that it would
emit these insertelements immediately after the PHI, even if there were
other PHIs after it.

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Index: lib/Transforms/Scalar/Scalarizer.cpp
===================================================================
--- lib/Transforms/Scalar/Scalarizer.cpp.orig
+++ lib/Transforms/Scalar/Scalarizer.cpp
@@ -638,8 +638,11 @@ bool Scalarizer::finish() {
       // InsertElements.
       Type *Ty = Op->getType();
       Value *Res = UndefValue::get(Ty);
+      BasicBlock *BB = Op->getParent();
       unsigned Count = Ty->getVectorNumElements();
-      IRBuilder<> Builder(Op->getParent(), Op);
+      IRBuilder<> Builder(BB, Op);
+      if (isa<PHINode>(Op))
+        Builder.SetInsertPoint(BB, BB->getFirstInsertionPt());
       for (unsigned I = 0; I < Count; ++I)
         Res = Builder.CreateInsertElement(Res, CV[I], Builder.getInt32(I),
                                           Op->getName() + ".upto" + Twine(I));
Index: test/Transforms/Scalarizer/basic.ll
===================================================================
--- test/Transforms/Scalarizer/basic.ll.orig
+++ test/Transforms/Scalarizer/basic.ll
@@ -414,6 +414,35 @@ define void @f13(<4 x float *> *%dest, <
   ret void
 }
 
+; Test combinations of vector and non-vector PHIs.
+define <4 x float> @f14(<4 x float> %acc, i32 %count) {
+; CHECK-LABEL: @f14(
+; CHECK: %this_acc.i0 = phi float [ %acc.i0, %entry ], [ %next_acc.i0, %loop ]
+; CHECK: %this_acc.i1 = phi float [ %acc.i1, %entry ], [ %next_acc.i1, %loop ]
+; CHECK: %this_acc.i2 = phi float [ %acc.i2, %entry ], [ %next_acc.i2, %loop ]
+; CHECK: %this_acc.i3 = phi float [ %acc.i3, %entry ], [ %next_acc.i3, %loop ]
+; CHECK: %this_count = phi i32 [ %count, %entry ], [ %next_count, %loop ]
+; CHECK: %this_acc.upto0 = insertelement <4 x float> undef, float %this_acc.i0, i32 0
+; CHECK: %this_acc.upto1 = insertelement <4 x float> %this_acc.upto0, float %this_acc.i1, i32 1
+; CHECK: %this_acc.upto2 = insertelement <4 x float> %this_acc.upto1, float %this_acc.i2, i32 2
+; CHECK: %this_acc = insertelement <4 x float> %this_acc.upto2, float %this_acc.i3, i32 3
+; CHECK: ret <4 x float> %next_acc
+entry:
+  br label %loop
+
+loop:
+  %this_acc = phi <4 x float> [ %acc, %entry ], [ %next_acc, %loop ]
+  %this_count = phi i32 [ %count, %entry ], [ %next_count, %loop ]
+  %foo = call <4 x float> @ext(<4 x float> %this_acc)
+  %next_acc = fadd <4 x float> %this_acc, %foo
+  %next_count = sub i32 %this_count, 1
+  %cmp = icmp eq i32 %next_count, 0
+  br i1 %cmp, label %loop, label %exit
+
+exit:
+  ret <4 x float> %next_acc
+}
+
 !0 = metadata !{ metadata !"root" }
 !1 = metadata !{ metadata !"set1", metadata !0 }
 !2 = metadata !{ metadata !"set2", metadata !0 }