[llvm] 3b6e250 - [TBAA] Only clear TBAAStruct if field can be extracted. (#81285)

[via llvm-commits]

Author: Florian Hahn
Date: 2024-02-16T09:49:21Z
New Revision: 3b6e25048f188692c27e7788f4e4453a3963306d

URL: https://github.com/llvm/llvm-project/commit/3b6e25048f188692c27e7788f4e4453a3963306d
DIFF: https://github.com/llvm/llvm-project/commit/3b6e25048f188692c27e7788f4e4453a3963306d.diff

LOG: [TBAA] Only clear TBAAStruct if field can be extracted. (#81285)

Retain TBAAStruct if we fail to match the access to a single field. All
users at the moment use this when using the full size of the original
access. SROA also retains the original TBAAStruct when accessing parts
at offset 0.

Motivation for this and follow-on patches is to improve codegen for
libc++, where using memcpy limits optimizations, like vectorization for
code iteration over std::vector<std::complex<float>>:
https://godbolt.org/z/f3vqYos3c

Depends on https://github.com/llvm/llvm-project/pull/81284

Added: 
    

Modified: 
    llvm/lib/Analysis/TypeBasedAliasAnalysis.cpp
    llvm/test/Transforms/InstCombine/struct-assign-tbaa.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Analysis/TypeBasedAliasAnalysis.cpp b/llvm/lib/Analysis/TypeBasedAliasAnalysis.cpp
index d05f42552e81de..bfd70414c0340c 100644
--- a/llvm/lib/Analysis/TypeBasedAliasAnalysis.cpp
+++ b/llvm/lib/Analysis/TypeBasedAliasAnalysis.cpp
@@ -821,14 +821,15 @@ MDNode *AAMDNodes::extendToTBAA(MDNode *MD, ssize_t Len) {
 AAMDNodes AAMDNodes::adjustForAccess(unsigned AccessSize) {
   AAMDNodes New = *this;
   MDNode *M = New.TBAAStruct;
-  New.TBAAStruct = nullptr;
   if (M && M->getNumOperands() == 3 && M->getOperand(0) &&
       mdconst::hasa<ConstantInt>(M->getOperand(0)) &&
       mdconst::extract<ConstantInt>(M->getOperand(0))->isZero() &&
       M->getOperand(1) && mdconst::hasa<ConstantInt>(M->getOperand(1)) &&
       mdconst::extract<ConstantInt>(M->getOperand(1))->getValue() ==
           AccessSize &&
-      M->getOperand(2) && isa<MDNode>(M->getOperand(2)))
+      M->getOperand(2) && isa<MDNode>(M->getOperand(2))) {
+    New.TBAAStruct = nullptr;
     New.TBAA = cast<MDNode>(M->getOperand(2));
+  }
   return New;
 }

diff  --git a/llvm/test/Transforms/InstCombine/struct-assign-tbaa.ll b/llvm/test/Transforms/InstCombine/struct-assign-tbaa.ll
index 1042c413fbb7bb..996d2c0e67e165 100644
--- a/llvm/test/Transforms/InstCombine/struct-assign-tbaa.ll
+++ b/llvm/test/Transforms/InstCombine/struct-assign-tbaa.ll
@@ -38,8 +38,8 @@ define ptr @test2() {
 define void @test3_multiple_fields(ptr nocapture %a, ptr nocapture %b) {
 ; CHECK-LABEL: @test3_multiple_fields(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[TMP0:%.*]] = load i64, ptr [[B:%.*]], align 4
-; CHECK-NEXT:    store i64 [[TMP0]], ptr [[A:%.*]], align 4
+; CHECK-NEXT:    [[TMP0:%.*]] = load i64, ptr [[B:%.*]], align 4, !tbaa.struct [[TBAA_STRUCT3:![0-9]+]]
+; CHECK-NEXT:    store i64 [[TMP0]], ptr [[A:%.*]], align 4, !tbaa.struct [[TBAA_STRUCT3]]
 ; CHECK-NEXT:    ret void
 ;
 entry:
@@ -86,4 +86,5 @@ entry:
 ; CHECK: [[TBAA0]] = !{[[META1:![0-9]+]], [[META1]], i64 0}
 ; CHECK: [[META1]] = !{!"float", [[META2:![0-9]+]]}
 ; CHECK: [[META2]] = !{!"Simple C/C++ TBAA"}
+; CHECK: [[TBAA_STRUCT3]] = !{i64 0, i64 4, [[TBAA0]], i64 4, i64 4, [[TBAA0]]}
 ;.