[PATCH] D142146: [IR] Avoid creation of GEPs into vectors (in one place)

[Jannik Silvanus via Phabricator via llvm-commits]

jsilvanus updated this revision to Diff 490628.
jsilvanus added a comment.

Review feedback: Simplify testcase by passing DL to opt


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D142146/new/

https://reviews.llvm.org/D142146

Files:
  llvm/lib/IR/DataLayout.cpp
  llvm/test/Transforms/InstCombine/load-gep-overalign.ll


Index: llvm/test/Transforms/InstCombine/load-gep-overalign.ll
===================================================================
--- llvm/test/Transforms/InstCombine/load-gep-overalign.ll
+++ llvm/test/Transforms/InstCombine/load-gep-overalign.ll
@@ -12,9 +12,7 @@
 ; OVERALIGNED and NATURAL should have the same result, because the layout of vectors ignores
 ; element type alignment, and thus the representation of @foo is the same in both cases.
 ;
-; TODO: The OVERALIGNED result is incorrect.
-; First, for nonzero even indices, the valid load is replaced by poison.
-; Second, the remaining bytes at indices >= 2 are also incorrect, as apparently padding bytes
+; TODO: The OVERALIGNED result is incorrect, as apparently padding bytes
 ; are assumed as they would appear in an array. In vectors, there is no padding.
 ;
 ; NATURAL-LABEL: @test_vector_load_i8(
@@ -31,11 +29,11 @@
 ; OVERALIGNED-LABEL: @test_vector_load_i8(
 ; OVERALIGNED-NEXT:    call void @report(i64 0, i8 1)
 ; OVERALIGNED-NEXT:    call void @report(i64 1, i8 35)
-; OVERALIGNED-NEXT:    call void @report(i64 2, i8 poison)
+; OVERALIGNED-NEXT:    call void @report(i64 2, i8 0)
 ; OVERALIGNED-NEXT:    call void @report(i64 3, i8 0)
-; OVERALIGNED-NEXT:    call void @report(i64 4, i8 poison)
+; OVERALIGNED-NEXT:    call void @report(i64 4, i8 69)
 ; OVERALIGNED-NEXT:    call void @report(i64 5, i8 103)
-; OVERALIGNED-NEXT:    call void @report(i64 6, i8 poison)
+; OVERALIGNED-NEXT:    call void @report(i64 6, i8 0)
 ; OVERALIGNED-NEXT:    call void @report(i64 7, i8 0)
 ; OVERALIGNED-NEXT:    ret void
 ;
Index: llvm/lib/IR/DataLayout.cpp
===================================================================
--- llvm/lib/IR/DataLayout.cpp
+++ llvm/lib/IR/DataLayout.cpp
@@ -937,13 +937,10 @@
   }
 
   if (auto *VecTy = dyn_cast<VectorType>(ElemTy)) {
-    ElemTy = VecTy->getElementType();
-    unsigned ElemSizeInBits = getTypeSizeInBits(ElemTy).getFixedValue();
-    // GEPs over non-multiple of 8 size vector elements are invalid.
-    if (ElemSizeInBits % 8 != 0)
-      return std::nullopt;
-
-    return getElementIndex(TypeSize::Fixed(ElemSizeInBits / 8), Offset);
+    // Vector GEPs are partially broken (e.g. for overaligned element types),
+    // and may be forbidden in the future, so avoid generating GEPs into
+    // vectors. See https://discourse.llvm.org/t/67497
+    return std::nullopt;
   }
 
   if (auto *STy = dyn_cast<StructType>(ElemTy)) {


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