Create a getelementptr instead of sub expr for ValueOffsetPair if the

value is a pointer.

This patch is to fix PR30213. When expanding an expr based on ValueOffsetPair,
if the value is of pointer type, we can only create a getelementptr instead
of sub expr.

Differential Revision: https://reviews.llvm.org/D24088

llvm-svn: 281439

1 files changed, 36 insertions, 0 deletions

diff --git a/llvm/test/Analysis/ScalarEvolution/scev-expander-reuse-gep.ll b/llvm/test/Analysis/ScalarEvolution/scev-expander-reuse-gep.ll
new file mode 100644
index 00000000000..fd47b0854bb
--- /dev/null
+++ b/llvm/test/Analysis/ScalarEvolution/scev-expander-reuse-gep.ll
@@ -0,0 +1,36 @@
+; PR30213. Check scev expand will generate correct code if the value
+; in ValueOffsetPair is of pointer type.
+; RUN: opt -mtriple=i386-apple-macosx10.12.0 < %s -loop-reduce -S | FileCheck %s
+
+; CHECK: %ptr4.ptr1 = select i1 %cmp.i, i8* %ptr4, i8* %ptr1
+; CHECK-NEXT: %scevgep = getelementptr i8, i8* %ptr4.ptr1, i32 1
+; CHECK-NEXT: br label %while.cond.i
+
+target datalayout = "e-m:o-p:32:32-f64:32:64-f80:128-n8:16:32-S128"
+target triple = "i386-apple-macosx10.12.0"
+
+; Function Attrs: nounwind optsize ssp
+define void @Foo() {
+entry:
+  switch i2 undef, label %sw.epilog102 [
+    i2 -2, label %sw.bb28
+  ]
+
+sw.bb28:                                          ; preds = %entry
+  %0 = load i8*, i8** undef, align 2
+  %ptr1 = getelementptr inbounds i8, i8* undef, i32 -1
+  %ptr4 = getelementptr inbounds i8, i8* %0, i32 -1
+  %cmp.i = icmp ult i8* undef, %0
+  %ptr4.ptr1 = select i1 %cmp.i, i8* %ptr4, i8* %ptr1
+  br label %while.cond.i
+
+while.cond.i:                                     ; preds = %while.cond.i, %sw.bb28
+  %currPtr.1.i = phi i8* [ %incdec.ptr.i, %while.cond.i ], [ %ptr4.ptr1, %sw.bb28 ]
+  %incdec.ptr.i = getelementptr inbounds i8, i8* %currPtr.1.i, i32 1
+  %1 = load i8, i8* %incdec.ptr.i, align 1
+  br label %while.cond.i
+
+sw.epilog102:                                     ; preds = %entry
+  unreachable
+}
+