Teach SCEVExpander to avoid creating over-indexed GEP indices when

possible. For example, it now emits

  %p.2.ip.1 = getelementptr [3 x [3 x double]]* %p, i64 2, i64 %tmp, i64 1

instead of the equivalent but less obvious

  %p.2.ip.1 = getelementptr [3 x [3 x double]]* %p, i64 0, i64 %tmp, i64 19


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@72452 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 19 insertions, 0 deletions

diff --git a/test/Transforms/IndVarSimplify/preserve-gep-remainder.ll b/test/Transforms/IndVarSimplify/preserve-gep-remainder.ll
new file mode 100644
index 0000000000..95726ea081
--- /dev/null
+++ b/test/Transforms/IndVarSimplify/preserve-gep-remainder.ll
@@ -0,0 +1,19 @@
+; RUN: llvm-as < %s | opt -indvars | llvm-dis \
+; RUN:   | grep {\[%\]p.2.ip.1 = getelementptr \\\[3 x \\\[3 x double\\\]\\\]\\* \[%\]p, i64 2, i64 \[%\]tmp, i64 1}
+
+; Indvars shouldn't expand this to
+;   %p.2.ip.1 = getelementptr [3 x [3 x double]]* %p, i64 0, i64 %tmp, i64 19
+; or something. That's valid, but more obscure.
+
+define void @foo([3 x [3 x double]]* noalias %p) nounwind {
+entry:
+  br label %loop
+
+loop:
+  %i = phi i64 [ 0, %entry ], [ %i.next, %loop ]
+  %ip = add i64 %i, 1
+  %p.2.ip.1 = getelementptr [3 x [3 x double]]* %p, i64 2, i64 %ip, i64 1
+  volatile store double 0.0, double* %p.2.ip.1
+  %i.next = add i64 %i, 1
+  br label %loop
+}