[MergeFuncs] Fix bug in merging GetElementPointers

[• jrkoenig]

Summary

GetElementPointers must have the first argument's type compared
for structural equivalence. Previously the code erroneously compared the
pointer's type, but this code was dead because all pointer types (of the
same address space) are the same. The pointee must be compared instead
(using the type stored in the GEP, not from the pointer type which will
be erased anyway).

[nlewycky]

LGTM

[jfb]

lgtm

llvm/trunk/lib/Transforms/IPO/MergeFunctions.cpp

int FunctionComparator::cmpGEPs(const GEPOperator *GEPL,
   // When we have target data, we can reduce the GEP down to the value in bytes
   // added to the address.
   const DataLayout &DL = FnL->getParent()->getDataLayout();
   unsigned BitWidth = DL.getPointerSizeInBits(ASL);
   APInt OffsetL(BitWidth, 0), OffsetR(BitWidth, 0);
   if (GEPL->accumulateConstantOffset(DL, OffsetL) &&
       GEPR->accumulateConstantOffset(DL, OffsetR))
     return cmpAPInts(OffsetL, OffsetR);
-  if (int Res = cmpTypes(GEPL->getPointerOperand()->getType(),
-                         GEPR->getPointerOperand()->getType()))
+  if (int Res = cmpTypes(GEPL->getSourceElementType(),
+                         GEPR->getSourceElementType()))
     return Res;
 
   if (int Res = cmpNumbers(GEPL->getNumOperands(), GEPR->getNumOperands()))
     return Res;
 
   for (unsigned i = 0, e = GEPL->getNumOperands(); i != e; ++i) {
     if (int Res = cmpValues(GEPL->getOperand(i), GEPR->getOperand(i)))
       return Res;

llvm/trunk/test/Transforms/MergeFunc/gep-base-type.ll

+; RUN: opt -mergefunc -S < %s | FileCheck %s
+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"
+
+; These should not be merged, the type of the GEP pointer argument does not have
+; the same stride.
+
+%"struct1" = type <{ i8*, i32, [4 x i8] }>
+%"struct2" = type { i8*, { i64, i64 } }
+
+define internal %struct2* @Ffunc(%struct2* %P, i64 %i) {
+; CHECK-LABEL: @Ffunc(
+; CHECK-NEXT: getelementptr
+; CHECK-NEXT: getelementptr
+; CHECK-NEXT: getelementptr
+; CHECK-NEXT: getelementptr
+; CHECK-NEXT: getelementptr
+; CHECK-NEXT: getelementptr
+; CHECK-NEXT: ret
+  %1 = getelementptr inbounds %"struct2", %"struct2"* %P, i64 %i
+  %2 = getelementptr inbounds %"struct2", %"struct2"* %P, i64 %i
+  %3 = getelementptr inbounds %"struct2", %"struct2"* %P, i64 %i
+  %4 = getelementptr inbounds %"struct2", %"struct2"* %P, i64 %i
+  %5 = getelementptr inbounds %"struct2", %"struct2"* %P, i64 %i
+  %6 = getelementptr inbounds %"struct2", %"struct2"* %P, i64 %i
+  ret %struct2* %6
+}
+
+
+define internal %struct1* @Gfunc(%struct1* %P, i64 %i) {
+; CHECK-LABEL: @Gfunc(
+; CHECK-NEXT: getelementptr
+; CHECK-NEXT: getelementptr
+; CHECK-NEXT: getelementptr
+; CHECK-NEXT: getelementptr
+; CHECK-NEXT: getelementptr
+; CHECK-NEXT: getelementptr
+; CHECK-NEXT: ret
+  %1 = getelementptr inbounds %"struct1", %"struct1"* %P, i64 %i
+  %2 = getelementptr inbounds %"struct1", %"struct1"* %P, i64 %i
+  %3 = getelementptr inbounds %"struct1", %"struct1"* %P, i64 %i
+  %4 = getelementptr inbounds %"struct1", %"struct1"* %P, i64 %i
+  %5 = getelementptr inbounds %"struct1", %"struct1"* %P, i64 %i
+  %6 = getelementptr inbounds %"struct1", %"struct1"* %P, i64 %i
+  ret %struct1* %6
+}
+