Make SimplifyDemandedVectorElts simplify vectors with multiple
users, and teach it about shufflevector instructions.
Also, fix a subtle bug in SimplifyDemandedVectorElts'
insertelement code.
This is a patch that was originally written by Eli Friedman,
with some fixes and cleanup by me.
llvm-svn: 55995
diff --git a/llvm/test/Transforms/InstCombine/pr2645.ll b/llvm/test/Transforms/InstCombine/pr2645.ll
new file mode 100644
index 0000000..04cc185
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/pr2645.ll
@@ -0,0 +1,33 @@
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep {insertelement <4 x float> undef}
+
+; Instcombine should be able to prove that none of the
+; insertelement's first operand's elements are needed.
+
+define internal void @""(i8*) {
+; <label>:1
+ bitcast i8* %0 to i32* ; <i32*>:2 [#uses=1]
+ load i32* %2, align 1 ; <i32>:3 [#uses=1]
+ getelementptr i8* %0, i32 4 ; <i8*>:4 [#uses=1]
+ bitcast i8* %4 to i32* ; <i32*>:5 [#uses=1]
+ load i32* %5, align 1 ; <i32>:6 [#uses=1]
+ br label %7
+
+; <label>:7 ; preds = %9, %1
+ %.01 = phi <4 x float> [ undef, %1 ], [ %12, %9 ] ; <<4 x float>> [#uses=1]
+ %.0 = phi i32 [ %3, %1 ], [ %15, %9 ] ; <i32> [#uses=3]
+ icmp slt i32 %.0, %6 ; <i1>:8 [#uses=1]
+ br i1 %8, label %9, label %16
+
+; <label>:9 ; preds = %7
+ sitofp i32 %.0 to float ; <float>:10 [#uses=1]
+ insertelement <4 x float> %.01, float %10, i32 0 ; <<4 x float>>:11 [#uses=1]
+ shufflevector <4 x float> %11, <4 x float> undef, <4 x i32> zeroinitializer ; <<4 x float>>:12 [#uses=2]
+ getelementptr i8* %0, i32 48 ; <i8*>:13 [#uses=1]
+ bitcast i8* %13 to <4 x float>* ; <<4 x float>*>:14 [#uses=1]
+ store <4 x float> %12, <4 x float>* %14, align 16
+ add i32 %.0, 2 ; <i32>:15 [#uses=1]
+ br label %7
+
+; <label>:16 ; preds = %7
+ ret void
+}