From 97bd39138671c26531e0c9276b13c74dad6387d1 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Thu, 27 May 2004 17:30:27 +0000
Subject: [PATCH] Fix InstCombine/load.ll & PR347.

This code hadn't been updated after the "structs with more than 256 elements"
related changes to the GEP instruction.  Also it was not handling the
ConstantAggregateZero class.

Now it does!

llvm-svn: 13834
---
 .../Scalar/InstructionCombining.cpp           | 36 ++++++++++++-------
 1 file changed, 24 insertions(+), 12 deletions(-)

diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 6d39c50e3fb..532747b0336 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -2852,19 +2852,31 @@ static Constant *GetGEPGlobalInitializer(Constant *C, ConstantExpr *CE) {
 
   // Loop over all of the operands, tracking down which value we are
   // addressing...
-  for (unsigned i = 2, e = CE->getNumOperands(); i != e; ++i)
-    if (ConstantUInt *CU = dyn_cast<ConstantUInt>(CE->getOperand(i))) {
-      ConstantStruct *CS = dyn_cast<ConstantStruct>(C);
-      if (CS == 0) return 0;
-      if (CU->getValue() >= CS->getValues().size()) return 0;
-      C = cast<Constant>(CS->getValues()[CU->getValue()]);
-    } else if (ConstantSInt *CS = dyn_cast<ConstantSInt>(CE->getOperand(i))) {
-      ConstantArray *CA = dyn_cast<ConstantArray>(C);
-      if (CA == 0) return 0;
-      if ((uint64_t)CS->getValue() >= CA->getValues().size()) return 0;
-      C = cast<Constant>(CA->getValues()[CS->getValue()]);
-    } else 
+  gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
+  for (++I; I != E; ++I)
+    if (const StructType *STy = dyn_cast<StructType>(*I)) {
+      ConstantUInt *CU = cast<ConstantUInt>(I.getOperand());
+      assert(CU->getValue() < STy->getNumElements() &&
+             "Struct index out of range!");
+      if (ConstantStruct *CS = dyn_cast<ConstantStruct>(C)) {
+        C = cast<Constant>(CS->getValues()[CU->getValue()]);
+      } else if (isa<ConstantAggregateZero>(C)) {
+	C = Constant::getNullValue(STy->getElementType(CU->getValue()));
+      } else {
+        return 0;
+      }
+    } else if (ConstantInt *CI = dyn_cast<ConstantInt>(I.getOperand())) {
+      const ArrayType *ATy = cast<ArrayType>(*I);
+      if ((uint64_t)CI->getRawValue() >= ATy->getNumElements()) return 0;
+      if (ConstantArray *CA = dyn_cast<ConstantArray>(C))
+        C = cast<Constant>(CA->getValues()[CI->getRawValue()]);
+      else if (isa<ConstantAggregateZero>(C))
+        C = Constant::getNullValue(ATy->getElementType());
+      else
+        return 0;
+    } else {
       return 0;
+    }
   return C;
 }