SROA: preserve alignment tags on loads and stores.

When splitting up an alloca's uses we were dropping any explicit
alignment tags, which means they default to the ABI-required default
alignment and this can cause miscompiles if the real value was smaller.

Also refactor the TBAA metadata into a parent class since it's shared by
both children anyway.

llvm-svn: 349465

1 files changed, 47 insertions, 0 deletions

diff --git a/llvm/test/Transforms/SROA/alignment.ll b/llvm/test/Transforms/SROA/alignment.ll
index 8bc90181246..cbae6be018c 100644
--- a/llvm/test/Transforms/SROA/alignment.ll
+++ b/llvm/test/Transforms/SROA/alignment.ll
@@ -181,3 +181,50 @@ entry:
   ret void
 ; CHECK: ret void
 }
+
+define void @test8() {
+; CHECK-LABEL: @test8(
+; CHECK: load i32, {{.*}}, align 1
+; CHECK: load i32, {{.*}}, align 1
+; CHECK: load i32, {{.*}}, align 1
+; CHECK: load i32, {{.*}}, align 1
+; CHECK: load i32, {{.*}}, align 1
+
+  %ptr = alloca [5 x i32], align 1
+  %ptr.8 = bitcast [5 x i32]* %ptr to i8*
+  call void @populate(i8* %ptr.8)
+  %val = load [5 x i32], [5 x i32]* %ptr, align 1
+  ret void
+}
+
+define void @test9() {
+; CHECK-LABEL: @test9(
+; CHECK: load i32, {{.*}}, align 8
+; CHECK: load i32, {{.*}}, align 4
+; CHECK: load i32, {{.*}}, align 8
+; CHECK: load i32, {{.*}}, align 4
+; CHECK: load i32, {{.*}}, align 8
+
+  %ptr = alloca [5 x i32], align 8
+  %ptr.8 = bitcast [5 x i32]* %ptr to i8*
+  call void @populate(i8* %ptr.8)
+  %val = load [5 x i32], [5 x i32]* %ptr, align 8
+  ret void
+}
+
+define void @test10() {
+; CHECK-LABEL: @test10(
+; CHECK: load i32, {{.*}}, align 2
+; CHECK: load i8, {{.*}}, align 2
+; CHECK: load i8, {{.*}}, align 1
+; CHECK: load i8, {{.*}}, align 2
+; CHECK: load i16, {{.*}}, align 2
+
+  %ptr = alloca {i32, i8, i8, {i8, i16}}, align 2
+  %ptr.8 = bitcast {i32, i8, i8, {i8, i16}}* %ptr to i8*
+  call void @populate(i8* %ptr.8)
+  %val = load {i32, i8, i8, {i8, i16}}, {i32, i8, i8, {i8, i16}}* %ptr, align 2
+  ret void
+}
+
+declare void @populate(i8*)