[PATCH] D104734: [llvm-diff] Explicitly check ConstantStructs for differences

[Bill Wendling via Phabricator via llvm-commits]

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A ConstantStruct is renamed when the LLVM context sees a new one. This
makes global variable initializers appear different when they aren't.
Instead, check the ConstantStruct for equivalence.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D104734

Files:
  llvm/test/tools/llvm-diff/initializers.ll
  llvm/tools/llvm-diff/DifferenceEngine.cpp


Index: llvm/tools/llvm-diff/DifferenceEngine.cpp
===================================================================
--- llvm/tools/llvm-diff/DifferenceEngine.cpp
+++ llvm/tools/llvm-diff/DifferenceEngine.cpp
@@ -404,6 +404,9 @@
     return false;
   }
 
+private:
+  std::vector<StringRef> StructStack;
+
 public:
   bool equivalentAsOperands(const Constant *L, const Constant *R) {
     // Use equality as a preliminary filter.
@@ -465,6 +468,34 @@
       return true;
     }
 
+    // If L and R are ConstantStructs, compare each field and type.
+    if (isa<ConstantStruct>(L)) {
+      const ConstantStruct *CSL = cast<ConstantStruct>(L);
+      const ConstantStruct *CSR = cast<ConstantStruct>(R);
+
+      if (CSL->getType()->getNumElements() != CSR->getType()->getNumElements())
+        return false;
+
+      StructStack.push_back(CSL->getName());
+
+      for (unsigned I = 0; I < CSL->getType()->getNumElements(); I++) {
+        const Value *LAgg = CSL->getAggregateElement(I);
+        const Value *RAgg = CSR->getAggregateElement(I);
+
+        if (std::find(StructStack.begin(), StructStack.end(),
+                      LAgg->getName()) != StructStack.end())
+          continue;
+
+        if (!equivalentAsOperands(LAgg, RAgg)) {
+          StructStack.pop_back();
+          return false;
+        }
+      }
+
+      StructStack.pop_back();
+      return true;
+    }
+
     return false;
   }
 
Index: llvm/test/tools/llvm-diff/initializers.ll
===================================================================
--- llvm/test/tools/llvm-diff/initializers.ll
+++ llvm/test/tools/llvm-diff/initializers.ll
@@ -10,3 +10,16 @@
   %1 = getelementptr [2 x i16*], [2 x i16*]* @gv2, i64 0, i64 undef
   ret void
 }
+
+; A named structure may be renamed when the right module is read. This is due
+; to the LLParser being different between the left and right modules, and the
+; context renaming one.
+
+%struct.ty1 = type { i16, i16 }
+
+ at gv3 = internal global [1 x %struct.ty1] [%struct.ty1 { i16 928, i16 0 }], align 16
+
+define void @bar() {
+  %1 = getelementptr [1 x %struct.ty1], [1 x %struct.ty1]* @gv3, i64 0, i64 undef
+  ret void
+}


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