[llvm] 50c523a - [InlineFunction] Only update noalias scopes once for an instruction.

[Jeroen Dobbelaere via llvm-commits]

Author: Jeroen Dobbelaere
Date: 2021-02-02T17:57:10+01:00
New Revision: 50c523a9d4402c69d59c0b2ecb383a763d16cde9

URL: https://github.com/llvm/llvm-project/commit/50c523a9d4402c69d59c0b2ecb383a763d16cde9
DIFF: https://github.com/llvm/llvm-project/commit/50c523a9d4402c69d59c0b2ecb383a763d16cde9.diff

LOG: [InlineFunction] Only update noalias scopes once for an instruction.

Inlining sometimes maps different instructions to be inlined onto the same instruction.

We must ensure to only remap the noalias scopes once. Otherwise the scope might disappear (at best).
This patch ensures that we only replace scopes for which the mapping is known.

This approach is preferred over tracking which instructions we already handled in a SmallPtrSet,
as that one will need more memory.

Reviewed By: nikic

Differential Revision: https://reviews.llvm.org/D95862

Added: 
    llvm/test/Transforms/Inline/noalias3.ll

Modified: 
    llvm/lib/Transforms/Utils/InlineFunction.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Utils/InlineFunction.cpp b/llvm/lib/Transforms/Utils/InlineFunction.cpp
index 0ac8fa537f4e..3026342cc4a6 100644
--- a/llvm/lib/Transforms/Utils/InlineFunction.cpp
+++ b/llvm/lib/Transforms/Utils/InlineFunction.cpp
@@ -921,14 +921,20 @@ void ScopedAliasMetadataDeepCloner::remap(ValueToValueMapTy &VMap) {
     if (!I)
       continue;
 
+    // Only update scopes when we find them in the map. If they are not, it is
+    // because we already handled that instruction before. This is faster than
+    // tracking which instructions we already updated.
     if (MDNode *M = I->getMetadata(LLVMContext::MD_alias_scope))
-      I->setMetadata(LLVMContext::MD_alias_scope, MDMap[M]);
+      if (MDNode *MNew = MDMap.lookup(M))
+        I->setMetadata(LLVMContext::MD_alias_scope, MNew);
 
     if (MDNode *M = I->getMetadata(LLVMContext::MD_noalias))
-      I->setMetadata(LLVMContext::MD_noalias, MDMap[M]);
+      if (MDNode *MNew = MDMap.lookup(M))
+        I->setMetadata(LLVMContext::MD_noalias, MNew);
 
     if (auto *Decl = dyn_cast<NoAliasScopeDeclInst>(I))
-      Decl->setScopeList(MDMap[Decl->getScopeList()]);
+      if (MDNode *MNew = MDMap.lookup(Decl->getScopeList()))
+        Decl->setScopeList(MNew);
   }
 }
 

diff  --git a/llvm/test/Transforms/Inline/noalias3.ll b/llvm/test/Transforms/Inline/noalias3.ll
new file mode 100644
index 000000000000..b94cbd6ab72f
--- /dev/null
+++ b/llvm/test/Transforms/Inline/noalias3.ll
@@ -0,0 +1,35 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --function-signature
+; RUN: opt -inline -S < %s | FileCheck %s
+
+define void @caller(i8* %ptr) {
+; CHECK-LABEL: define {{[^@]+}}@caller
+; CHECK-SAME: (i8* [[PTR:%.*]]) {
+; CHECK-NEXT:    [[I_I:%.*]] = load i8, i8* [[PTR]], align 1, !alias.scope !0
+; CHECK-NEXT:    ret void
+;
+  call void @callee(i8* %ptr)
+  ret void
+}
+
+define void @callee(i8* %ptr) {
+; CHECK-LABEL: define {{[^@]+}}@callee
+; CHECK-SAME: (i8* [[PTR:%.*]]) {
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[I:%.*]] = load i8, i8* [[PTR]], align 1, !alias.scope !3
+; CHECK-NEXT:    br label [[DUMMY:%.*]]
+; CHECK:       dummy:
+; CHECK-NEXT:    [[I_COPY:%.*]] = phi i8 [ [[I]], [[ENTRY:%.*]] ]
+; CHECK-NEXT:    ret void
+;
+entry:
+  %i = load i8, i8* %ptr, !alias.scope !0
+  br label %dummy
+
+dummy:
+  %i.copy = phi i8 [ %i, %entry ]
+  ret void
+}
+
+!0 = !{!1}
+!1 = distinct !{!1, !2}
+!2 = distinct !{!2}