[CodeGen] Use index type for pointer offset in replaceStoreOfInsertLoad

Also use getMemBasePlusOffset rather than a raw ADD since that won't
work for capability types either.

Fixes: 38e1851 ("[DAGCombine] Fold (store (insert_elt (load p)) x p) -> (store x)")

Author: jrtc27

llvm/test/CodeGen/CHERI-Generic/Inputs/store-insert-load-index-type.ll

@@ -0,0 +1,14 @@
+; RUN: llc @PURECAP_HARDFLOAT_ARGS@ -O0 < %s | FileCheck %s
+
+;; Test that, when DAGCombiner folds a load-insert-store to just storing the
+;; element, it uses the index rather than pointer type for the offset. Without
+;; this it would crash with:
+;;
+;;    Assertion `Int.isZero() && "Should not create non-zero capability " "constants with SelectionDAG::getConstant()"' failed.
+define void @foo(ptr addrspace(200) %p) addrspace(200) {
+entry:
+  %0 = load <4 x i8>, ptr addrspace(200) %p, align 4
+  %1 = insertelement <4 x i8> %0, i8 0, i64 0
+  store <4 x i8> %1, ptr addrspace(200) %p, align 4
+  ret void
+}

llvm/test/CodeGen/CHERI-Generic/MIPS/store-insert-load-index-type.ll

@@ -0,0 +1,22 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --scrub-attributes --version 2
+; DO NOT EDIT -- This file was generated from test/CodeGen/CHERI-Generic/Inputs/store-insert-load-index-type.ll
+; RUN: llc -mtriple=mips64 -mcpu=cheri128 -mattr=+cheri128 --relocation-model=pic -target-abi purecap -O0 < %s | FileCheck %s
+
+;; Test that, when DAGCombiner folds a load-insert-store to just storing the
+;; element, it uses the index rather than pointer type for the offset. Without
+;; this it would crash with:
+;;
+;;    Assertion `Int.isZero() && "Should not create non-zero capability " "constants with SelectionDAG::getConstant()"' failed.
+define void @foo(ptr addrspace(200) %p) addrspace(200) {
+; CHECK-LABEL: foo:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    daddiu $1, $zero, 0
+; CHECK-NEXT:    csb $zero, $zero, 0($c3)
+; CHECK-NEXT:    cjr $c17
+; CHECK-NEXT:    nop
+entry:
+  %0 = load <4 x i8>, ptr addrspace(200) %p, align 4
+  %1 = insertelement <4 x i8> %0, i8 0, i64 0
+  store <4 x i8> %1, ptr addrspace(200) %p, align 4
+  ret void
+}

llvm/test/CodeGen/CHERI-Generic/RISCV32/store-insert-load-index-type.ll

@@ -0,0 +1,22 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
+; DO NOT EDIT -- This file was generated from test/CodeGen/CHERI-Generic/Inputs/store-insert-load-index-type.ll
+; RUN: llc -mtriple=riscv32 --relocation-model=pic -target-abi il32pc64f -mattr=+xcheri,+xcheripurecap,+f -O0 < %s | FileCheck %s
+
+;; Test that, when DAGCombiner folds a load-insert-store to just storing the
+;; element, it uses the index rather than pointer type for the offset. Without
+;; this it would crash with:
+;;
+;;    Assertion `Int.isZero() && "Should not create non-zero capability " "constants with SelectionDAG::getConstant()"' failed.
+define void @foo(ptr addrspace(200) %p) addrspace(200) {
+; CHECK-LABEL: foo:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    cmove a1, a0
+; CHECK-NEXT:    li a0, 0
+; CHECK-NEXT:    csb a0, 0(a1)
+; CHECK-NEXT:    cret
+entry:
+  %0 = load <4 x i8>, ptr addrspace(200) %p, align 4
+  %1 = insertelement <4 x i8> %0, i8 0, i64 0
+  store <4 x i8> %1, ptr addrspace(200) %p, align 4
+  ret void
+}

llvm/test/CodeGen/CHERI-Generic/RISCV64/store-insert-load-index-type.ll

@@ -0,0 +1,22 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
+; DO NOT EDIT -- This file was generated from test/CodeGen/CHERI-Generic/Inputs/store-insert-load-index-type.ll
+; RUN: llc -mtriple=riscv64 --relocation-model=pic -target-abi l64pc128d -mattr=+xcheri,+xcheripurecap,+f,+d -O0 < %s | FileCheck %s
+
+;; Test that, when DAGCombiner folds a load-insert-store to just storing the
+;; element, it uses the index rather than pointer type for the offset. Without
+;; this it would crash with:
+;;
+;;    Assertion `Int.isZero() && "Should not create non-zero capability " "constants with SelectionDAG::getConstant()"' failed.
+define void @foo(ptr addrspace(200) %p) addrspace(200) {
+; CHECK-LABEL: foo:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    cmove a1, a0
+; CHECK-NEXT:    li a0, 0
+; CHECK-NEXT:    csb a0, 0(a1)
+; CHECK-NEXT:    cret
+entry:
+  %0 = load <4 x i8>, ptr addrspace(200) %p, align 4
+  %1 = insertelement <4 x i8> %0, i8 0, i64 0
+  store <4 x i8> %1, ptr addrspace(200) %p, align 4
+  ret void
+}