[llvm] 90ad786 - [IR] Prefer scalar type for struct indexes in GEP constant expressions.

[Eli Friedman via llvm-commits]

Author: Eli Friedman
Date: 2020-06-23T16:14:36-07:00
New Revision: 90ad786947cc861756c95238f96c267b2a3c4849

URL: https://github.com/llvm/llvm-project/commit/90ad786947cc861756c95238f96c267b2a3c4849
DIFF: https://github.com/llvm/llvm-project/commit/90ad786947cc861756c95238f96c267b2a3c4849.diff

LOG: [IR] Prefer scalar type for struct indexes in GEP constant expressions.

This has two advantages: one, it's simpler, and two, it doesn't require
heroic pattern matching with scalable vectors.

Also includes a small fix to DataLayout to allow the scalable vector
testcase to work correctly.

Differential Revision: https://reviews.llvm.org/D82061

Added: 
    

Modified: 
    llvm/lib/IR/Constants.cpp
    llvm/lib/IR/DataLayout.cpp
    llvm/test/Analysis/ConstantFolding/vectorgep-crash.ll
    llvm/test/Transforms/InstSimplify/gep.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/IR/Constants.cpp b/llvm/lib/IR/Constants.cpp
index daa15bb2a9b0..1afd73d95f56 100644
--- a/llvm/lib/IR/Constants.cpp
+++ b/llvm/lib/IR/Constants.cpp
@@ -2175,15 +2175,20 @@ Constant *ConstantExpr::getGetElementPtr(Type *Ty, Constant *C,
   std::vector<Constant*> ArgVec;
   ArgVec.reserve(1 + Idxs.size());
   ArgVec.push_back(C);
-  for (unsigned i = 0, e = Idxs.size(); i != e; ++i) {
+  auto GTI = gep_type_begin(Ty, Idxs), GTE = gep_type_end(Ty, Idxs);
+  for (; GTI != GTE; ++GTI) {
+    auto *Idx = cast<Constant>(GTI.getOperand());
     assert(
-        (!isa<VectorType>(Idxs[i]->getType()) ||
-         cast<VectorType>(Idxs[i]->getType())->getElementCount() == EltCount) &&
+        (!isa<VectorType>(Idx->getType()) ||
+         cast<VectorType>(Idx->getType())->getElementCount() == EltCount) &&
         "getelementptr index type missmatch");
 
-    Constant *Idx = cast<Constant>(Idxs[i]);
-    if (EltCount.Min != 0 && !Idxs[i]->getType()->isVectorTy())
+    if (GTI.isStruct() && Idx->getType()->isVectorTy()) {
+      Idx = Idx->getSplatValue();
+    } else if (GTI.isSequential() && EltCount.Min != 0 &&
+               !Idx->getType()->isVectorTy()) {
       Idx = ConstantVector::getSplat(EltCount, Idx);
+    }
     ArgVec.push_back(Idx);
   }
 

diff  --git a/llvm/lib/IR/DataLayout.cpp b/llvm/lib/IR/DataLayout.cpp
index 0fe3199b9b49..a4c39a5ca994 100644
--- a/llvm/lib/IR/DataLayout.cpp
+++ b/llvm/lib/IR/DataLayout.cpp
@@ -814,7 +814,7 @@ Type *DataLayout::getIndexType(Type *Ty) const {
   unsigned NumBits = getIndexTypeSizeInBits(Ty);
   IntegerType *IntTy = IntegerType::get(Ty->getContext(), NumBits);
   if (VectorType *VecTy = dyn_cast<VectorType>(Ty))
-    return FixedVectorType::get(IntTy, VecTy->getNumElements());
+    return VectorType::get(IntTy, VecTy);
   return IntTy;
 }
 

diff  --git a/llvm/test/Analysis/ConstantFolding/vectorgep-crash.ll b/llvm/test/Analysis/ConstantFolding/vectorgep-crash.ll
index b2faf89c2b7f..1562d74d83aa 100644
--- a/llvm/test/Analysis/ConstantFolding/vectorgep-crash.ll
+++ b/llvm/test/Analysis/ConstantFolding/vectorgep-crash.ll
@@ -24,7 +24,7 @@ top:
 
 @G = internal global [65 x %struct.A] zeroinitializer, align 16
 ; CHECK-LABEL: @test
-; CHECK: ret <16 x i32*> getelementptr ([65 x %struct.A], [65 x %struct.A]* @G, <16 x i64> zeroinitializer, <16 x i64> <i64 1, i64 2, i64 3, i64 4, i64 5, i64 6, i64 7, i64 8, i64 9, i64 10, i64 11, i64 12, i64 13, i64 14, i64 15, i64 16>, <16 x i32> zeroinitializer)
+; CHECK: ret <16 x i32*> getelementptr ([65 x %struct.A], [65 x %struct.A]* @G, <16 x i64> zeroinitializer, <16 x i64> <i64 1, i64 2, i64 3, i64 4, i64 5, i64 6, i64 7, i64 8, i64 9, i64 10, i64 11, i64 12, i64 13, i64 14, i64 15, i64 16>, i32 0)
 define <16 x i32*> @test() {
 vector.body:
   %VectorGep = getelementptr [65 x %struct.A], [65 x %struct.A]* @G, <16 x i64> zeroinitializer, <16 x i64> <i64 1, i64 2, i64 3, i64 4, i64 5, i64 6, i64 7, i64 8, i64 9, i64 10, i64 11, i64 12, i64 13, i64 14, i64 15, i64 16>, <16 x i32> zeroinitializer

diff  --git a/llvm/test/Transforms/InstSimplify/gep.ll b/llvm/test/Transforms/InstSimplify/gep.ll
index c4fa8df717cc..ea5e72e7f755 100644
--- a/llvm/test/Transforms/InstSimplify/gep.ll
+++ b/llvm/test/Transforms/InstSimplify/gep.ll
@@ -152,7 +152,7 @@ define <4 x i32*> @vector_idx_vector() {
 %struct = type { double, float }
 define <4 x float*> @vector_idx_mix_scalar_vector() {
 ; CHECK-LABEL: @vector_idx_mix_scalar_vector(
-; CHECK-NEXT:    ret <4 x float*> getelementptr (%struct, <4 x %struct*> zeroinitializer, <4 x i64> zeroinitializer, <4 x i32> <i32 1, i32 1, i32 1, i32 1>)
+; CHECK-NEXT:    ret <4 x float*> getelementptr (%struct, <4 x %struct*> zeroinitializer, <4 x i64> zeroinitializer, i32 1)
 ;
   %gep = getelementptr %struct, <4 x %struct*> zeroinitializer, i32 0, <4 x i32> <i32 1, i32 1, i32 1, i32 1>
   ret <4 x float*> %gep
@@ -168,4 +168,12 @@ define <vscale x 4 x i32*> @scalable_idx_scalar() {
   ret <vscale x 4 x i32*> %gep
 }
 
+define <vscale x 4 x float*> @scalable_vector_idx_mix_scalar_vector() {
+; CHECK-LABEL: @scalable_vector_idx_mix_scalar_vector(
+; CHECK-NEXT:    ret <vscale x 4 x float*> getelementptr (%struct, <vscale x 4 x %struct*> zeroinitializer, <vscale x 4 x i64> zeroinitializer, i32 1)
+;
+  %gep = getelementptr %struct, <vscale x 4 x %struct*> zeroinitializer, i32 0, i32 1
+  ret <vscale x 4 x float*> %gep
+}
+
 ; Check ConstantExpr::getGetElementPtr() using ElementCount for size queries - end.