Teach BaseIndexOffset::match to identify base pointers in loops.

The small utility function that pattern matches Base + Index +
Offset patterns for loads and stores fails to recognize the base
pointer for loads/stores from/into an array at offset 0 inside a
loop. As a result DAGCombiner::MergeConsecutiveStores was not able
to merge all stores.

This commit fixes the issue by adding an additional pattern match
and also a test case.

Reviewer: Nadav
llvm-svn: 188936

1 files changed, 30 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/X86/merge_store.ll b/llvm/test/CodeGen/X86/merge_store.ll
new file mode 100644
index 00000000000..940688c6252
--- /dev/null
+++ b/llvm/test/CodeGen/X86/merge_store.ll
@@ -0,0 +1,30 @@
+; RUN: llc < %s -mtriple=x86_64-unknown-unknown -mcpu=x86-64 | FileCheck %s
+
+define void @merge_store(i32* nocapture %a) {
+; CHECK-LABEL: merge_store:
+; CHECK: movq
+; CHECK: movq
+entry:
+  br label %for.body
+
+  for.body:
+  %indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
+  %arrayidx = getelementptr inbounds i32* %a, i64 %indvars.iv
+  store i32 1, i32* %arrayidx, align 4
+  %0 = or i64 %indvars.iv, 1
+  %arrayidx2 = getelementptr inbounds i32* %a, i64 %0
+  store i32 1, i32* %arrayidx2, align 4
+  %1 = or i64 %indvars.iv, 2
+  %arrayidx5 = getelementptr inbounds i32* %a, i64 %1
+  store i32 1, i32* %arrayidx5, align 4
+  %2 = or i64 %indvars.iv, 3
+  %arrayidx8 = getelementptr inbounds i32* %a, i64 %2
+  store i32 1, i32* %arrayidx8, align 4
+  %indvars.iv.next = add nuw nsw i64 %indvars.iv, 4
+  %3 = trunc i64 %indvars.iv.next to i32
+  %cmp = icmp slt i32 %3, 1000
+  br i1 %cmp, label %for.body, label %for.end
+
+  for.end:
+  ret void
+}