Make SROA produce a vector only when the alloca is actually

accessed at least once as a vector.  This prevents it from
compiling the example in not-a-vector into:

define double @test(double %A, double %B) {
	%tmp4 = insertelement <7 x double> undef, double %A, i32 0
	%tmp = insertelement <7 x double> %tmp4, double %B, i32 4
	%tmp2 = extractelement <7 x double> %tmp, i32 4
	ret double %tmp2
}

instead, producing the integer code.  Producing vectors when they
aren't otherwise in the program is dangerous because a lot of other
code treats them carefully and doesn't want to break them down.
OTOH, many things want to break down tasty i448's.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@63638 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 19 insertions, 0 deletions

diff --git a/test/Transforms/ScalarRepl/not-a-vector.ll b/test/Transforms/ScalarRepl/not-a-vector.ll
new file mode 100644
index 0000000000..e2111e7b31
--- /dev/null
+++ b/test/Transforms/ScalarRepl/not-a-vector.ll
@@ -0,0 +1,19 @@
+; RUN: llvm-as < %s | opt -scalarrepl | llvm-dis | not grep alloca
+; RUN: llvm-as < %s | opt -scalarrepl | llvm-dis | not grep {7 x double}
+; RUN: llvm-as < %s | opt -scalarrepl -instcombine | llvm-dis | grep {ret double %B}
+
+define double @test(double %A, double %B) {
+	%ARR = alloca [7 x i64]
+	%C = bitcast [7 x i64]* %ARR to double*
+	store double %A, double* %C
+
+	%D = getelementptr [7 x i64]* %ARR, i32 0, i32 4
+	%E = bitcast i64* %D to double*
+	store double %B, double* %E
+
+	%F = getelementptr double* %C, i32 4
+	%G = load double* %F
+	ret double %G
+}
+
+