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.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@55995 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 33 insertions, 0 deletions

diff --git a/test/Transforms/InstCombine/pr2645.ll b/test/Transforms/InstCombine/pr2645.ll
new file mode 100644
index 0000000000..04cc1852cb
--- /dev/null
+++ b/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
+}