Adding a width of the GEP index to the Data Layout.

Making a width of GEP Index, which is used for address calculation, to be one of the pointer properties in the Data Layout.
p[address space]:size:memory_size:alignment:pref_alignment:index_size_in_bits.
The index size parameter is optional, if not specified, it is equal to the pointer size.

Till now, the InstCombiner normalized GEPs and extended the Index operand to the pointer width.
It works fine if you can convert pointer to integer for address calculation and all registered targets do this.
But some ISAs have very restricted instruction set for the pointer calculation. During discussions were desided to retrieve information for GEP index from the Data Layout.
http://lists.llvm.org/pipermail/llvm-dev/2018-January/120416.html

I added an interface to the Data Layout and I changed the InstCombiner and some other passes to take the Index width into account.
This change does not affect any in-tree target. I added tests to cover data layouts with explicitly specified index size.

Differential Revision: https://reviews.llvm.org/D42123

llvm-svn: 325102

1 files changed, 20 insertions, 20 deletions

diff --git a/llvm/lib/Analysis/ConstantFolding.cpp b/llvm/lib/Analysis/ConstantFolding.cpp
index e88b8f14d54..ace7131e7d5 100644
--- a/llvm/lib/Analysis/ConstantFolding.cpp
+++ b/llvm/lib/Analysis/ConstantFolding.cpp
@@ -286,7 +286,7 @@ bool llvm::IsConstantOffsetFromGlobal(Constant *C, GlobalValue *&GV,
                                       APInt &Offset, const DataLayout &DL) {
   // Trivial case, constant is the global.
   if ((GV = dyn_cast<GlobalValue>(C))) {
-    unsigned BitWidth = DL.getPointerTypeSizeInBits(GV->getType());
+    unsigned BitWidth = DL.getIndexTypeSizeInBits(GV->getType());
     Offset = APInt(BitWidth, 0);
     return true;
   }
@@ -305,7 +305,7 @@ bool llvm::IsConstantOffsetFromGlobal(Constant *C, GlobalValue *&GV,
   if (!GEP)
     return false;
 
-  unsigned BitWidth = DL.getPointerTypeSizeInBits(GEP->getType());
+  unsigned BitWidth = DL.getIndexTypeSizeInBits(GEP->getType());
   APInt TmpOffset(BitWidth, 0);
 
   // If the base isn't a global+constant, we aren't either.
@@ -808,26 +808,26 @@ Constant *SymbolicallyEvaluateGEP(const GEPOperator *GEP,
   // If this is a constant expr gep that is effectively computing an
   // "offsetof", fold it into 'cast int Size to T*' instead of 'gep 0, 0, 12'
   for (unsigned i = 1, e = Ops.size(); i != e; ++i)
-    if (!isa<ConstantInt>(Ops[i])) {
-
-      // If this is "gep i8* Ptr, (sub 0, V)", fold this as:
-      // "inttoptr (sub (ptrtoint Ptr), V)"
-      if (Ops.size() == 2 && ResElemTy->isIntegerTy(8)) {
-        auto *CE = dyn_cast<ConstantExpr>(Ops[1]);
-        assert((!CE || CE->getType() == IntPtrTy) &&
-               "CastGEPIndices didn't canonicalize index types!");
-        if (CE && CE->getOpcode() == Instruction::Sub &&
-            CE->getOperand(0)->isNullValue()) {
-          Constant *Res = ConstantExpr::getPtrToInt(Ptr, CE->getType());
-          Res = ConstantExpr::getSub(Res, CE->getOperand(1));
-          Res = ConstantExpr::getIntToPtr(Res, ResTy);
-          if (auto *FoldedRes = ConstantFoldConstant(Res, DL, TLI))
-            Res = FoldedRes;
-          return Res;
+      if (!isa<ConstantInt>(Ops[i])) {
+
+        // If this is "gep i8* Ptr, (sub 0, V)", fold this as:
+        // "inttoptr (sub (ptrtoint Ptr), V)"
+        if (Ops.size() == 2 && ResElemTy->isIntegerTy(8)) {
+          auto *CE = dyn_cast<ConstantExpr>(Ops[1]);
+          assert((!CE || CE->getType() == IntPtrTy) &&
+                 "CastGEPIndices didn't canonicalize index types!");
+          if (CE && CE->getOpcode() == Instruction::Sub &&
+              CE->getOperand(0)->isNullValue()) {
+            Constant *Res = ConstantExpr::getPtrToInt(Ptr, CE->getType());
+            Res = ConstantExpr::getSub(Res, CE->getOperand(1));
+            Res = ConstantExpr::getIntToPtr(Res, ResTy);
+            if (auto *FoldedRes = ConstantFoldConstant(Res, DL, TLI))
+              Res = FoldedRes;
+            return Res;
+          }
         }
+        return nullptr;
       }
-      return nullptr;
-    }
 
   unsigned BitWidth = DL.getTypeSizeInBits(IntPtrTy);
   APInt Offset =