[Transforms] Propagate new-format TBAA tags on simplification of memo…

…ry-transfer intrinsics

With this patch in place, when a new-format TBAA tag is available
for a memory-transfer intrinsic call, we prefer propagating that
new-format tag. Otherwise, we fallback to the old approach where
we try to construct a proper TBAA access tag from 'tbaa.struct'
metadata.

Differential Revision: https://reviews.llvm.org/D41543

llvm-svn: 325488

llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp

@@ -227,7 +227,9 @@ Instruction *InstCombiner::SimplifyMemTransfer(MemIntrinsic *MI) {
   // If the memcpy has metadata describing the members, see if we can get the
   // TBAA tag describing our copy.
   MDNode *CopyMD = nullptr;
-  if (MDNode *M = MI->getMetadata(LLVMContext::MD_tbaa_struct)) {
+  if (MDNode *M = MI->getMetadata(LLVMContext::MD_tbaa)) {
+    CopyMD = M;
+  } else if (MDNode *M = MI->getMetadata(LLVMContext::MD_tbaa_struct)) {
     if (M->getNumOperands() == 3 && M->getOperand(0) &&
         mdconst::hasa<ConstantInt>(M->getOperand(0)) &&
         mdconst::extract<ConstantInt>(M->getOperand(0))->isZero() &&

llvm/test/Transforms/InstCombine/struct-assign-tbaa-new.ll

@@ -0,0 +1,53 @@
+; RUN: opt -instcombine -S < %s | FileCheck %s
+;
+; Verify that instcombine preserves TBAA tags when converting a memcpy into
+; a scalar load and store.
+
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
+
+declare void @llvm.memcpy.p0i8.p0i8.i64(i8* nocapture, i8* nocapture, i64, i1) nounwind
+
+%A = type { float }
+
+define void @test1(%A* %a1, %A* %a2) {
+entry:
+; CHECK-LABEL: @test1
+; CHECK: %[[LOAD:.*]] = load i32, {{.*}}, !tbaa [[TAG_A:!.*]]
+; CHECK: store i32 %[[LOAD]], {{.*}}, !tbaa [[TAG_A]]
+; CHECK: ret
+  %0 = bitcast %A* %a1 to i8*
+  %1 = bitcast %A* %a2 to i8*
+  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 4 %0, i8* align 4 %1, i64 4, i1 false), !tbaa !4  ; TAG_A
+  ret void
+}
+
+%B = type { i32 (i8*, i32*, double*)** }
+
+define i32 (i8*, i32*, double*)*** @test2() {
+; CHECK-LABEL: @test2
+; CHECK-NOT: memcpy
+; CHECK: ret
+  %tmp = alloca %B, align 8
+  %tmp1 = bitcast %B* %tmp to i8*
+  call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 8 %tmp1, i8* align 8 undef, i64 8, i1 false), !tbaa !7  ; TAG_B
+  %tmp2 = getelementptr %B, %B* %tmp, i32 0, i32 0
+  %tmp3 = load i32 (i8*, i32*, double*)**, i32 (i8*, i32*, double*)*** %tmp2
+  ret i32 (i8*, i32*, double*)*** %tmp2
+}
+
+!0 = !{!"root"}
+!1 = !{!0, !"char"}
+!2 = !{!1, !"float"}
+!3 = !{!1, i64 4, !"A", !2, i64 0, i64 4}
+!4 = !{!3, !3, i64 0, i64 4}
+!5 = !{!1, !"pointer"}
+!6 = !{!1, i64 8, !"B", !5, i64 0, i64 8}
+!7 = !{!6, !6, i64 0, i64 8}
+
+; CHECK-DAG: [[ROOT:!.*]] = !{!"root"}
+; CHECK-DAG: [[TYPE_char:!.*]] = !{[[ROOT]], !"char"}
+; CHECK-DAG: [[TYPE_float:!.*]] = !{[[TYPE_char]], !"float"}
+; CHECK-DAG: [[TYPE_A:!.*]] = !{[[TYPE_char]], i64 4, !"A", [[TYPE_float]], i64 0, i64 4}
+; CHECK-DAG: [[TAG_A]] = !{[[TYPE_A]], [[TYPE_A]], i64 0, i64 4}
+; Note that the memcpy() call in test2() transforms into an
+; undecorated 'store undef', so TAG_B is not present in the output.