[llvm] 6a834d2 - [ConstraintElim] Use collectOffset instead of custom GEP idx iteration.

[Florian Hahn via llvm-commits]

Author: Florian Hahn
Date: 2022-11-28T16:54:58Z
New Revision: 6a834d2f2b962619a8ab7a8aa1e79033ddaeb8cf

URL: https://github.com/llvm/llvm-project/commit/6a834d2f2b962619a8ab7a8aa1e79033ddaeb8cf
DIFF: https://github.com/llvm/llvm-project/commit/6a834d2f2b962619a8ab7a8aa1e79033ddaeb8cf.diff

LOG: [ConstraintElim] Use collectOffset instead of custom GEP idx iteration.

Use collectOffset to collect scaled indices and constant offset for GEP
instead of custom code. This simplifies the logic in decomposeGEP and
allows to handle all cases supported by the generic helper.

Added: 
    

Modified: 
    llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
    llvm/test/Transforms/ConstraintElimination/constants-unsigned-predicates.ll
    llvm/test/Transforms/ConstraintElimination/gep-arithmetic.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp b/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
index 624420a9cad13..f823a38ca14b0 100644
--- a/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
+++ b/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
@@ -270,34 +270,18 @@ decomposeGEP(GetElementPtrInst &GEP,
     return Result;
   }
 
-  Decomposition Result = GEP.getPointerOperand();
-  gep_type_iterator GTI = gep_type_begin(GEP);
-  for (User::const_op_iterator I = GEP.op_begin() + 1, E = GEP.op_end(); I != E;
-       ++I, ++GTI) {
-    Value *Index = *I;
-
-    // Bail out for scalable vectors for now.
-    if (isa<ScalableVectorType>(GTI.getIndexedType()))
-      return &GEP;
-
-    // Struct indices must be constants (and reference an existing field). Add
-    // them to the constant factor.
-    if (StructType *STy = GTI.getStructTypeOrNull()) {
-      // For a struct, add the member offset.
-      unsigned FieldNo = cast<ConstantInt>(Index)->getZExtValue();
-      if (FieldNo == 0)
-        continue;
-
-      // Add offset to constant factor.
-      Result.add(int64_t(DL.getStructLayout(STy)->getElementOffset(FieldNo)));
-      continue;
-    }
-
-    // For an array/pointer, add the element offset, explicitly scaled.
-    unsigned Scale = DL.getTypeAllocSize(GTI.getIndexedType()).getFixedSize();
+  Type *PtrTy = GEP.getType()->getScalarType();
+  unsigned BitWidth = DL.getIndexTypeSizeInBits(PtrTy);
+  MapVector<Value *, APInt> VariableOffsets;
+  APInt ConstantOffset(BitWidth, 0);
+  if (!GEP.collectOffset(DL, BitWidth, VariableOffsets, ConstantOffset))
+    return &GEP;
 
+  Decomposition Result(ConstantOffset.getSExtValue(),
+                       DecompEntry(1, GEP.getPointerOperand()));
+  for (auto [Index, Scale] : VariableOffsets) {
     auto IdxResult = decompose(Index, Preconditions, IsSigned, DL);
-    IdxResult.mul(Scale);
+    IdxResult.mul(Scale.getSExtValue());
     Result.add(IdxResult);
 
     // If Op0 is signed non-negative, the GEP is increasing monotonically and

diff  --git a/llvm/test/Transforms/ConstraintElimination/constants-unsigned-predicates.ll b/llvm/test/Transforms/ConstraintElimination/constants-unsigned-predicates.ll
index e6aa6f6a88bf9..86c7dd375bf71 100644
--- a/llvm/test/Transforms/ConstraintElimination/constants-unsigned-predicates.ll
+++ b/llvm/test/Transforms/ConstraintElimination/constants-unsigned-predicates.ll
@@ -52,7 +52,7 @@ define i1 @test_ult_gep_2(ptr %base) {
 ; CHECK-LABEL: @test_ult_gep_2(
 ; CHECK-NEXT:    [[GEP_SUB_1:%.*]] = getelementptr inbounds i8, ptr [[BASE:%.*]], i8 -1
 ; CHECK-NEXT:    [[C_1:%.*]] = icmp ult ptr [[BASE]], [[GEP_SUB_1]]
-; CHECK-NEXT:    ret i1 [[C_1]]
+; CHECK-NEXT:    ret i1 false
 ;
   %gep.sub.1 = getelementptr inbounds i8, ptr %base, i8 -1
   %c.1 = icmp ult ptr %base, %gep.sub.1

diff  --git a/llvm/test/Transforms/ConstraintElimination/gep-arithmetic.ll b/llvm/test/Transforms/ConstraintElimination/gep-arithmetic.ll
index fbbb37ffbcd1d..2978b83ebc2a8 100644
--- a/llvm/test/Transforms/ConstraintElimination/gep-arithmetic.ll
+++ b/llvm/test/Transforms/ConstraintElimination/gep-arithmetic.ll
@@ -81,12 +81,12 @@ define i1 @gep_constant_negative_index(ptr %dst, ptr %lower, ptr %upper) {
 ; CHECK-NEXT:    [[CMP_DST_SUB_4_LOWER:%.*]] = icmp uge ptr [[DST_SUB_4]], [[LOWER]]
 ; CHECK-NEXT:    [[CMP_DST_SUB_4_UPPER:%.*]] = icmp ult ptr [[DST_SUB_4]], [[UPPER]]
 ; CHECK-NEXT:    [[RES_4:%.*]] = xor i1 [[RES_3]], [[CMP_DST_SUB_4_LOWER]]
-; CHECK-NEXT:    [[RES_5:%.*]] = xor i1 [[RES_4]], [[CMP_DST_SUB_4_UPPER]]
+; CHECK-NEXT:    [[RES_5:%.*]] = xor i1 [[RES_4]], true
 ; CHECK-NEXT:    [[DST_SUB_5:%.*]] = getelementptr inbounds i8, ptr [[DST]], i64 -5
 ; CHECK-NEXT:    [[CMP_DST_SUB_5_LOWER:%.*]] = icmp uge ptr [[DST_SUB_5]], [[LOWER]]
 ; CHECK-NEXT:    [[CMP_DST_SUB_5_UPPER:%.*]] = icmp ult ptr [[DST_SUB_5]], [[UPPER]]
 ; CHECK-NEXT:    [[RES_6:%.*]] = xor i1 [[RES_5]], [[CMP_DST_SUB_5_LOWER]]
-; CHECK-NEXT:    [[RES_7:%.*]] = xor i1 [[RES_6]], [[CMP_DST_SUB_5_UPPER]]
+; CHECK-NEXT:    [[RES_7:%.*]] = xor i1 [[RES_6]], true
 ; CHECK-NEXT:    ret i1 [[RES_7]]
 ; CHECK:       else:
 ; CHECK-NEXT:    [[ELSE_CMP_DST_LOWER:%.*]] = icmp uge ptr [[DST]], [[LOWER]]