[InstCombine] Retain TBAA when narrowing memory accesses

Summary:
As discussed on the mailing list it is legal to propagate TBAA to loads/stores
from/to smaller regions of a larger load tagged with TBAA. Do so for
(load->extractvalue)=>(gep->load) and similar foldings.

Reviewed By: sanjoy
Differential Revision: https://reviews.llvm.org/D31954

llvm-svn: 306615

1 files changed, 45 insertions, 0 deletions

diff --git a/llvm/test/Transforms/InstCombine/extractinsert-tbaa.ll b/llvm/test/Transforms/InstCombine/extractinsert-tbaa.ll
new file mode 100644
index 00000000000..b2a3a1a1bf9
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/extractinsert-tbaa.ll
@@ -0,0 +1,45 @@
+; RUN: opt -S -instcombine %s -o - | FileCheck %s
+
+%Complex = type { double, double }
+
+; Check that instcombine preserves TBAA when narrowing loads
+define double @teststructextract(%Complex *%val) {
+; CHECK: load double, {{.*}}, !tbaa
+; CHECK-NOT: load %Complex
+    %loaded = load %Complex, %Complex *%val, !tbaa !1
+    %real = extractvalue %Complex %loaded, 0
+    ret double %real
+}
+
+define double @testarrayextract([2 x double] *%val) {
+; CHECK: load double, {{.*}}, !tbaa
+; CHECK-NOT: load [2 x double]
+    %loaded = load [2 x double], [2 x double] *%val, !tbaa !1
+    %real = extractvalue [2 x double] %loaded, 0
+    ret double %real
+}
+
+; Check that inscombine preserves TBAA when breaking up stores
+define void @teststructinsert(%Complex *%loc, double %a, double %b) {
+; CHECK: store double %a, {{.*}}, !tbaa
+; CHECK: store double %b, {{.*}}, !tbaa
+; CHECK-NOT: store %Complex
+    %inserted  = insertvalue %Complex undef,      double %a, 0
+    %inserted2 = insertvalue %Complex %inserted,  double %b, 1
+    store %Complex %inserted2, %Complex *%loc, !tbaa !1
+    ret void
+}
+
+define void @testarrayinsert([2 x double] *%loc, double %a, double %b) {
+; CHECK: store double %a, {{.*}}, !tbaa
+; CHECK: store double %b, {{.*}}, !tbaa
+; CHECK-NOT: store [2 x double]
+    %inserted  = insertvalue [2 x double] undef,      double %a, 0
+    %inserted2 = insertvalue [2 x double] %inserted,  double %b, 1
+    store [2 x double] %inserted2, [2 x double] *%loc, !tbaa !1
+    ret void
+}
+
+!0 = !{!"tbaa_root"}
+!1 = !{!2, !2, i64 0}
+!2 = !{!"Complex", !0, i64 0}