[IR] Require index width to be ule pointer width (#70015)

I don't think there is a use case for having an index type that is wider
than the pointer type, and I'm not entirely clear what semantics this
would even have.

Also clarify the GEP semantics to explicitly say how they interact with
the index type width.

Author: nikic

llvm/docs/LangRef.rst

@@ -2883,7 +2883,8 @@ as follows:
     This specifies the *size* of a pointer and its ``<abi>`` and
     ``<pref>``\erred alignments for address space ``n``. ``<pref>`` is optional
     and defaults to ``<abi>``. The fourth parameter ``<idx>`` is the size of the
-    index that used for address calculation. If not
+    index that used for address calculation, which must be less than or equal
+    to the pointer size. If not
     specified, the default index size is equal to the pointer size. All sizes
     are in bits. The address space, ``n``, is optional, and if not specified,
     denotes the default address space 0. The value of ``n`` must be
@@ -11030,6 +11031,24 @@ for the given testcase is equivalent to:
       ret ptr %t5
     }
 
+The indices are first converted to offsets in the pointer's index type. If the
+currently indexed type is a struct type, the struct offset corresponding to the
+index is sign-extended or truncated to the pointer index type. Otherwise, the
+index itself is sign-extended or truncated, and then multiplied by the type
+allocation size (that is, the size rounded up to the ABI alignment) of the
+currently indexed type.
+
+The offsets are then added to the low bits of the base address up to the index
+type width, with silently-wrapping two's complement arithmetic. If the pointer
+size is larger than the index size, this means that the bits outside the index
+type width will not be affected.
+
+The result value of the ``getelementptr`` may be outside the object pointed
+to by the base pointer. The result value may not necessarily be used to access
+memory though, even if it happens to point into allocated storage. See the
+:ref:`Pointer Aliasing Rules <pointeraliasing>` section for more
+information.
+
 If the ``inbounds`` keyword is present, the result value of a
 ``getelementptr`` with any non-zero indices is a
 :ref:`poison value <poisonvalues>` if one of the following rules is violated:
@@ -11061,16 +11080,6 @@ These rules are based on the assumption that no allocated object may cross
 the unsigned address space boundary, and no allocated object may be larger
 than half the pointer index type space.
 
-If the ``inbounds`` keyword is not present, the offsets are added to the
-base address with silently-wrapping two's complement arithmetic. If the
-offsets have a different width from the pointer's index type, they are
-sign-extended or truncated to the width of the pointer's index type. The result
-value of the ``getelementptr`` may be outside the object pointed to by the base
-pointer. The result value may not necessarily be used to access memory
-though, even if it happens to point into allocated storage. See the
-:ref:`Pointer Aliasing Rules <pointeraliasing>` section for more
-information.
-
 If the ``inrange`` keyword is present before any index, loading from or
 storing to any pointer derived from the ``getelementptr`` has undefined
 behavior if the load or store would access memory outside of the bounds of

llvm/lib/IR/DataLayout.cpp

@@ -649,6 +649,8 @@ Error DataLayout::setPointerAlignmentInBits(uint32_t AddrSpace, Align ABIAlign,
   if (PrefAlign < ABIAlign)
     return reportError(
         "Preferred alignment cannot be less than the ABI alignment");
+  if (IndexBitWidth > TypeBitWidth)
+    return reportError("Index width cannot be larger than pointer width");
 
   auto I = lower_bound(Pointers, AddrSpace,
                        [](const PointerAlignElem &A, uint32_t AddressSpace) {

llvm/test/Analysis/ScalarEvolution/ptrtoint-constantexpr-loop.ll

@@ -2,7 +2,6 @@
 ; RUN: opt < %s --data-layout="p:64:64:64:64" -S -disable-output "-passes=print<scalar-evolution>" 2>&1 | FileCheck --check-prefixes=PTR64_IDX64 %s
 ; RUN: opt < %s --data-layout="p:64:64:64:32" -S -disable-output "-passes=print<scalar-evolution>" 2>&1 | FileCheck --check-prefixes=PTR64_IDX32 %s
 ; RUN: opt < %s --data-layout="p:16:16:16:16" -S -disable-output "-passes=print<scalar-evolution>" 2>&1 | FileCheck --check-prefixes=PTR16_IDX16 %s
-; RUN: opt < %s --data-layout="p:16:16:16:32" -S -disable-output "-passes=print<scalar-evolution>" 2>&1 | FileCheck --check-prefixes=PTR16_IDX32 %s
 
 @global = external hidden global [0 x i8]
 
@@ -63,24 +62,6 @@ define hidden ptr @trunc_ptr_to_i64(ptr %arg, ptr %arg10) {
 ; PTR16_IDX16-NEXT:  Loop %bb11: Unpredictable symbolic max backedge-taken count.
 ; PTR16_IDX16-NEXT:  Loop %bb11: Unpredictable predicated backedge-taken count.
 ;
-; PTR16_IDX32-LABEL: 'trunc_ptr_to_i64'
-; PTR16_IDX32-NEXT:  Classifying expressions for: @trunc_ptr_to_i64
-; PTR16_IDX32-NEXT:    %tmp = phi i32 [ 0, %bb ], [ %tmp18, %bb17 ]
-; PTR16_IDX32-NEXT:    --> {0,+,2}<%bb11> U: [0,-1) S: [-2147483648,2147483647) Exits: <<Unknown>> LoopDispositions: { %bb11: Computable }
-; PTR16_IDX32-NEXT:    %tmp12 = getelementptr i8, ptr %arg, i64 ptrtoint (ptr @global to i64)
-; PTR16_IDX32-NEXT:    --> ((trunc i64 ptrtoint (ptr @global to i64) to i32) + %arg) U: [0,131071) S: [0,131071) Exits: ((trunc i64 ptrtoint (ptr @global to i64) to i32) + %arg) LoopDispositions: { %bb11: Invariant }
-; PTR16_IDX32-NEXT:    %tmp13 = bitcast ptr %tmp12 to ptr
-; PTR16_IDX32-NEXT:    --> ((trunc i64 ptrtoint (ptr @global to i64) to i32) + %arg) U: [0,131071) S: [0,131071) Exits: ((trunc i64 ptrtoint (ptr @global to i64) to i32) + %arg) LoopDispositions: { %bb11: Invariant }
-; PTR16_IDX32-NEXT:    %tmp14 = load i32, ptr %tmp13, align 4
-; PTR16_IDX32-NEXT:    --> %tmp14 U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %bb11: Variant }
-; PTR16_IDX32-NEXT:    %tmp18 = add i32 %tmp, 2
-; PTR16_IDX32-NEXT:    --> {2,+,2}<%bb11> U: [0,-1) S: [-2147483648,2147483647) Exits: <<Unknown>> LoopDispositions: { %bb11: Computable }
-; PTR16_IDX32-NEXT:  Determining loop execution counts for: @trunc_ptr_to_i64
-; PTR16_IDX32-NEXT:  Loop %bb11: Unpredictable backedge-taken count.
-; PTR16_IDX32-NEXT:  Loop %bb11: Unpredictable constant max backedge-taken count.
-; PTR16_IDX32-NEXT:  Loop %bb11: Unpredictable symbolic max backedge-taken count.
-; PTR16_IDX32-NEXT:  Loop %bb11: Unpredictable predicated backedge-taken count.
-;
 bb:
   br label %bb11
 
@@ -154,24 +135,6 @@ define hidden ptr @trunc_ptr_to_i32(ptr %arg, ptr %arg10) {
 ; PTR16_IDX16-NEXT:  Loop %bb11: Unpredictable symbolic max backedge-taken count.
 ; PTR16_IDX16-NEXT:  Loop %bb11: Unpredictable predicated backedge-taken count.
 ;
-; PTR16_IDX32-LABEL: 'trunc_ptr_to_i32'
-; PTR16_IDX32-NEXT:  Classifying expressions for: @trunc_ptr_to_i32
-; PTR16_IDX32-NEXT:    %tmp = phi i32 [ 0, %bb ], [ %tmp18, %bb17 ]
-; PTR16_IDX32-NEXT:    --> {0,+,2}<%bb11> U: [0,-1) S: [-2147483648,2147483647) Exits: <<Unknown>> LoopDispositions: { %bb11: Computable }
-; PTR16_IDX32-NEXT:    %tmp12 = getelementptr i8, ptr %arg, i32 ptrtoint (ptr @global to i32)
-; PTR16_IDX32-NEXT:    --> (ptrtoint (ptr @global to i32) + %arg) U: [0,131071) S: [0,131071) Exits: (ptrtoint (ptr @global to i32) + %arg) LoopDispositions: { %bb11: Invariant }
-; PTR16_IDX32-NEXT:    %tmp13 = bitcast ptr %tmp12 to ptr
-; PTR16_IDX32-NEXT:    --> (ptrtoint (ptr @global to i32) + %arg) U: [0,131071) S: [0,131071) Exits: (ptrtoint (ptr @global to i32) + %arg) LoopDispositions: { %bb11: Invariant }
-; PTR16_IDX32-NEXT:    %tmp14 = load i32, ptr %tmp13, align 4
-; PTR16_IDX32-NEXT:    --> %tmp14 U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %bb11: Variant }
-; PTR16_IDX32-NEXT:    %tmp18 = add i32 %tmp, 2
-; PTR16_IDX32-NEXT:    --> {2,+,2}<%bb11> U: [0,-1) S: [-2147483648,2147483647) Exits: <<Unknown>> LoopDispositions: { %bb11: Computable }
-; PTR16_IDX32-NEXT:  Determining loop execution counts for: @trunc_ptr_to_i32
-; PTR16_IDX32-NEXT:  Loop %bb11: Unpredictable backedge-taken count.
-; PTR16_IDX32-NEXT:  Loop %bb11: Unpredictable constant max backedge-taken count.
-; PTR16_IDX32-NEXT:  Loop %bb11: Unpredictable symbolic max backedge-taken count.
-; PTR16_IDX32-NEXT:  Loop %bb11: Unpredictable predicated backedge-taken count.
-;
 bb:
   br label %bb11
 
@@ -245,24 +208,6 @@ define hidden ptr @trunc_ptr_to_i128(ptr %arg, ptr %arg10) {
 ; PTR16_IDX16-NEXT:  Loop %bb11: Unpredictable symbolic max backedge-taken count.
 ; PTR16_IDX16-NEXT:  Loop %bb11: Unpredictable predicated backedge-taken count.
 ;
-; PTR16_IDX32-LABEL: 'trunc_ptr_to_i128'
-; PTR16_IDX32-NEXT:  Classifying expressions for: @trunc_ptr_to_i128
-; PTR16_IDX32-NEXT:    %tmp = phi i32 [ 0, %bb ], [ %tmp18, %bb17 ]
-; PTR16_IDX32-NEXT:    --> {0,+,2}<%bb11> U: [0,-1) S: [-2147483648,2147483647) Exits: <<Unknown>> LoopDispositions: { %bb11: Computable }
-; PTR16_IDX32-NEXT:    %tmp12 = getelementptr i8, ptr %arg, i128 ptrtoint (ptr @global to i128)
-; PTR16_IDX32-NEXT:    --> ((trunc i128 ptrtoint (ptr @global to i128) to i32) + %arg) U: [0,131071) S: [0,131071) Exits: ((trunc i128 ptrtoint (ptr @global to i128) to i32) + %arg) LoopDispositions: { %bb11: Invariant }
-; PTR16_IDX32-NEXT:    %tmp13 = bitcast ptr %tmp12 to ptr
-; PTR16_IDX32-NEXT:    --> ((trunc i128 ptrtoint (ptr @global to i128) to i32) + %arg) U: [0,131071) S: [0,131071) Exits: ((trunc i128 ptrtoint (ptr @global to i128) to i32) + %arg) LoopDispositions: { %bb11: Invariant }
-; PTR16_IDX32-NEXT:    %tmp14 = load i32, ptr %tmp13, align 4
-; PTR16_IDX32-NEXT:    --> %tmp14 U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %bb11: Variant }
-; PTR16_IDX32-NEXT:    %tmp18 = add i32 %tmp, 2
-; PTR16_IDX32-NEXT:    --> {2,+,2}<%bb11> U: [0,-1) S: [-2147483648,2147483647) Exits: <<Unknown>> LoopDispositions: { %bb11: Computable }
-; PTR16_IDX32-NEXT:  Determining loop execution counts for: @trunc_ptr_to_i128
-; PTR16_IDX32-NEXT:  Loop %bb11: Unpredictable backedge-taken count.
-; PTR16_IDX32-NEXT:  Loop %bb11: Unpredictable constant max backedge-taken count.
-; PTR16_IDX32-NEXT:  Loop %bb11: Unpredictable symbolic max backedge-taken count.
-; PTR16_IDX32-NEXT:  Loop %bb11: Unpredictable predicated backedge-taken count.
-;
 bb:
   br label %bb11
 
@@ -319,18 +264,6 @@ define void @zext_ptr_to_i32(i32 %arg, i32 %arg6) {
 ; PTR16_IDX16-NEXT:  Loop %bb7: Unpredictable symbolic max backedge-taken count.
 ; PTR16_IDX16-NEXT:  Loop %bb7: Unpredictable predicated backedge-taken count.
 ;
-; PTR16_IDX32-LABEL: 'zext_ptr_to_i32'
-; PTR16_IDX32-NEXT:  Classifying expressions for: @zext_ptr_to_i32
-; PTR16_IDX32-NEXT:    %tmp = sub i32 %arg, ptrtoint (ptr @global to i32)
-; PTR16_IDX32-NEXT:    --> ((-1 * ptrtoint (ptr @global to i32))<nsw> + %arg) U: full-set S: full-set Exits: ((-1 * ptrtoint (ptr @global to i32))<nsw> + %arg) LoopDispositions: { %bb7: Invariant }
-; PTR16_IDX32-NEXT:    %tmp9 = select i1 %tmp8, i16 0, i16 1
-; PTR16_IDX32-NEXT:    --> %tmp9 U: [0,2) S: [0,2) Exits: <<Unknown>> LoopDispositions: { %bb7: Variant }
-; PTR16_IDX32-NEXT:  Determining loop execution counts for: @zext_ptr_to_i32
-; PTR16_IDX32-NEXT:  Loop %bb7: Unpredictable backedge-taken count.
-; PTR16_IDX32-NEXT:  Loop %bb7: Unpredictable constant max backedge-taken count.
-; PTR16_IDX32-NEXT:  Loop %bb7: Unpredictable symbolic max backedge-taken count.
-; PTR16_IDX32-NEXT:  Loop %bb7: Unpredictable predicated backedge-taken count.
-;
 bb:
   br label %bb7
 
@@ -382,18 +315,6 @@ define void @sext_to_i32(i32 %arg, i32 %arg6) {
 ; PTR16_IDX16-NEXT:  Loop %bb7: Unpredictable symbolic max backedge-taken count.
 ; PTR16_IDX16-NEXT:  Loop %bb7: Unpredictable predicated backedge-taken count.
 ;
-; PTR16_IDX32-LABEL: 'sext_to_i32'
-; PTR16_IDX32-NEXT:  Classifying expressions for: @sext_to_i32
-; PTR16_IDX32-NEXT:    %tmp = sub i32 %arg, sext (i16 ptrtoint (ptr @global to i16) to i32)
-; PTR16_IDX32-NEXT:    --> ((-1 * (sext i16 ptrtoint (ptr @global to i16) to i32))<nsw> + %arg) U: full-set S: full-set Exits: ((-1 * (sext i16 ptrtoint (ptr @global to i16) to i32))<nsw> + %arg) LoopDispositions: { %bb7: Invariant }
-; PTR16_IDX32-NEXT:    %tmp9 = select i1 %tmp8, i16 0, i16 1
-; PTR16_IDX32-NEXT:    --> %tmp9 U: [0,2) S: [0,2) Exits: <<Unknown>> LoopDispositions: { %bb7: Variant }
-; PTR16_IDX32-NEXT:  Determining loop execution counts for: @sext_to_i32
-; PTR16_IDX32-NEXT:  Loop %bb7: Unpredictable backedge-taken count.
-; PTR16_IDX32-NEXT:  Loop %bb7: Unpredictable constant max backedge-taken count.
-; PTR16_IDX32-NEXT:  Loop %bb7: Unpredictable symbolic max backedge-taken count.
-; PTR16_IDX32-NEXT:  Loop %bb7: Unpredictable predicated backedge-taken count.
-;
 bb:
   br label %bb7
 
@@ -463,24 +384,6 @@ define i64 @sext_like_noop(i32 %n) {
 ; PTR16_IDX16-NEXT:   Predicates:
 ; PTR16_IDX16:       Loop %for.body: Trip multiple is 1
 ;
-; PTR16_IDX32-LABEL: 'sext_like_noop'
-; PTR16_IDX32-NEXT:  Classifying expressions for: @sext_like_noop
-; PTR16_IDX32-NEXT:    %ii = sext i32 %i to i64
-; PTR16_IDX32-NEXT:    --> (sext i32 {1,+,1}<nuw><%for.body> to i64) U: [-2147483648,2147483648) S: [-2147483648,2147483648) --> (-1 + (zext i32 ptrtoint (ptr @sext_like_noop to i32) to i64))<nsw> U: [-1,65535) S: [-1,65535)
-; PTR16_IDX32-NEXT:    %div = sdiv i64 55555, %ii
-; PTR16_IDX32-NEXT:    --> %div U: full-set S: full-set
-; PTR16_IDX32-NEXT:    %i = phi i32 [ %inc, %for.body ], [ 1, %entry ]
-; PTR16_IDX32-NEXT:    --> {1,+,1}<nuw><%for.body> U: [1,0) S: [1,0) Exits: (-1 + ptrtoint (ptr @sext_like_noop to i32))<nsw> LoopDispositions: { %for.body: Computable }
-; PTR16_IDX32-NEXT:    %inc = add nuw i32 %i, 1
-; PTR16_IDX32-NEXT:    --> {2,+,1}<nuw><%for.body> U: [2,0) S: [2,0) Exits: ptrtoint (ptr @sext_like_noop to i32) LoopDispositions: { %for.body: Computable }
-; PTR16_IDX32-NEXT:  Determining loop execution counts for: @sext_like_noop
-; PTR16_IDX32-NEXT:  Loop %for.body: backedge-taken count is (-2 + ptrtoint (ptr @sext_like_noop to i32))<nsw>
-; PTR16_IDX32-NEXT:  Loop %for.body: constant max backedge-taken count is -1
-; PTR16_IDX32-NEXT:  Loop %for.body: symbolic max backedge-taken count is (-2 + ptrtoint (ptr @sext_like_noop to i32))<nsw>
-; PTR16_IDX32-NEXT:  Loop %for.body: Predicated backedge-taken count is (-2 + ptrtoint (ptr @sext_like_noop to i32))<nsw>
-; PTR16_IDX32-NEXT:   Predicates:
-; PTR16_IDX32:       Loop %for.body: Trip multiple is 1
-;
 entry:
   %cmp6 = icmp sgt i32 %n, 1
   br label %for.body

llvm/test/Assembler/invalid-datalayout-index-size.ll

@@ -0,0 +1,3 @@
+; RUN: not llvm-as < %s 2>&1 | FileCheck %s
+target datalayout = "p:64:64:64:128"
+; CHECK: Index width cannot be larger than pointer width

llvm/test/Transforms/InferAlignment/ptrmask.ll

@@ -1,7 +1,7 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 2
 ; RUN: opt < %s -passes=infer-alignment -S | FileCheck %s
 
-target datalayout = "p1:64:64:64:32-p2:64:64:64:128"
+target datalayout = "p1:64:64:64:32"
 
 ; ------------------------------------------------------------------------------
 ; load instructions
@@ -88,18 +88,5 @@ define i8 @smaller_index_type(ptr addrspace(1) %ptr) {
   ret i8 %load
 }
 
-define i8 @larger_index_type(ptr addrspace(2) %ptr) {
-; CHECK-LABEL: define i8 @larger_index_type
-; CHECK-SAME: (ptr addrspace(2) [[PTR:%.*]]) {
-; CHECK-NEXT:    [[PTR2:%.*]] = call ptr addrspace(2) @llvm.ptrmask.p2.i128(ptr addrspace(2) [[PTR]], i128 -4)
-; CHECK-NEXT:    [[LOAD:%.*]] = load i8, ptr addrspace(2) [[PTR2]], align 4
-; CHECK-NEXT:    ret i8 [[LOAD]]
-;
-  %ptr2 = call ptr addrspace(2) @llvm.ptrmask.p2.i128(ptr addrspace(2) %ptr, i128 -4)
-  %load = load i8, ptr addrspace(2) %ptr2, align 1
-  ret i8 %load
-}
-
 declare ptr @llvm.ptrmask.p0.i64(ptr, i64)
 declare ptr addrspace(1) @llvm.ptrmask.p1.i32(ptr addrspace(1), i32)
-declare ptr addrspace(2) @llvm.ptrmask.p2.i128(ptr addrspace(2), i128)

mlir/test/Target/LLVMIR/Import/data-layout.ll

@@ -36,11 +36,11 @@ target datalayout = "e-m:e-p270:32:64-p271:32:32-p272:64:64-i64:64-f80:128-n8:16
 ; CHECK: dlti.dl_spec =
 ; CHECK: #dlti.dl_spec<
 ; CHECK-DAG:   #dlti.dl_entry<"dlti.endianness", "big">
-; CHECK-DAG:   #dlti.dl_entry<!llvm.ptr<270>, dense<[16, 32, 64, 128]> : vector<4xi32>>
+; CHECK-DAG:   #dlti.dl_entry<!llvm.ptr<270>, dense<[16, 32, 64, 8]> : vector<4xi32>>
 ; CHECK-DAG:   #dlti.dl_entry<!llvm.ptr<271>, dense<[16, 32, 64, 16]> : vector<4xi32>>
 ; CHECK-DAG:   #dlti.dl_entry<"dlti.alloca_memory_space", 1 : ui32>
 ; CHECK-DAG:   #dlti.dl_entry<i64, dense<[64, 128]> : vector<2xi32>>
-target datalayout = "A1-E-p270:16:32:64:128-p271:16:32:64-i64:64:128"
+target datalayout = "A1-E-p270:16:32:64:8-p271:16:32:64-i64:64:128"
 
 ; // -----
 

mlir/test/Target/LLVMIR/data-layout.mlir

@@ -7,7 +7,7 @@
 // CHECK: i64:64:128
 // CHECK: f80:128:256
 // CHECK: p0:32:64:128
-// CHECK: p1:32:32:32:64
+// CHECK: p1:32:32:32:16
 module attributes {dlti.dl_spec = #dlti.dl_spec<
 #dlti.dl_entry<"dlti.endianness", "big">,
 #dlti.dl_entry<"dlti.alloca_memory_space", 4 : ui32>,
@@ -16,7 +16,7 @@ module attributes {dlti.dl_spec = #dlti.dl_spec<
 #dlti.dl_entry<i64, dense<[64,128]> : vector<2xi32>>,
 #dlti.dl_entry<f80, dense<[128,256]> : vector<2xi32>>,
 #dlti.dl_entry<!llvm.ptr, dense<[32,64,128]> : vector<3xi32>>,
-#dlti.dl_entry<!llvm.ptr<1>, dense<[32,32,32,64]> : vector<4xi32>>
+#dlti.dl_entry<!llvm.ptr<1>, dense<[32,32,32,16]> : vector<4xi32>>
 >} {
   llvm.func @foo() {
     llvm.return