[llvm-branch-commits] [ConstantFolding] Avoid use of isNonIntegralPointerType() (PR #159959)

[Alexander Richardson via llvm-branch-commits]

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@@ -0,0 +1,75 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -S -passes=instsimplify < %s | FileCheck %s
+;; Check that we do not create new inttoptr intstructions for unstable pointers
+;; or pointers with external state (even if the values are all constants).
+;; NOTE: for all but the zero address space, the GEP should only modify the low 8 bits of the pointer.
+target datalayout = "p:16:16:16:16-p1:16:16:16:8-pu2:16:16:16:8-pe3:16:16:16:8"
+
+define ptr @test_null_base_normal() {
+; CHECK-LABEL: define ptr @test_null_base_normal() {
+; CHECK-NEXT:    ret ptr inttoptr (i16 -2 to ptr)
+;
+  %gep = getelementptr i8, ptr null, i8 -2
+  ret ptr %gep
+}
+define ptr @test_inttoptr_base_normal() {
+; CHECK-LABEL: define ptr @test_inttoptr_base_normal() {
+; CHECK-NEXT:    ret ptr null
+;
+  %base = inttoptr i16 -1 to ptr
+  %gep = getelementptr i8, ptr %base, i8 1
+  ret ptr %gep
+}
+
+;; Transformation is fine for non-integral address space, but we can only change
+;; the index bits (i8 -2 == i16 254)
+define ptr addrspace(1) @test_null_base_nonintegral() {
+; CHECK-LABEL: define ptr addrspace(1) @test_null_base_nonintegral() {
+; CHECK-NEXT:    ret ptr addrspace(1) inttoptr (i16 254 to ptr addrspace(1))
+;
+  %gep = getelementptr i8, ptr addrspace(1) null, i8 -2
+  ret ptr addrspace(1) %gep
+}
+define ptr addrspace(1) @test_inttoptr_base_nonintegral() {
+; CHECK-LABEL: define ptr addrspace(1) @test_inttoptr_base_nonintegral() {
+; CHECK-NEXT:    ret ptr addrspace(1) inttoptr (i16 -256 to ptr addrspace(1))
+;
+  %base = inttoptr i16 -1 to ptr addrspace(1)
+  %gep = getelementptr i8, ptr addrspace(1) %base, i8 1
+  ret ptr addrspace(1) %gep
+}
+
+;; For unstable pointers we should avoid any introduction of inttoptr
+define ptr addrspace(2) @test_null_base_unstable() {
+; CHECK-LABEL: define ptr addrspace(2) @test_null_base_unstable() {
+; CHECK-NEXT:    ret ptr addrspace(2) getelementptr (i8, ptr addrspace(2) null, i8 -2)
+;
+  %gep = getelementptr i8, ptr addrspace(2) null, i8 -2
+  ret ptr addrspace(2) %gep
+}
+define ptr addrspace(2) @test_inttoptr_base_unstable() {
+; CHECK-LABEL: define ptr addrspace(2) @test_inttoptr_base_unstable() {
+; CHECK-NEXT:    ret ptr addrspace(2) getelementptr (i8, ptr addrspace(2) inttoptr (i16 -1 to ptr addrspace(2)), i8 1)
+;
+  %base = inttoptr i16 -1 to ptr addrspace(2)
+  %gep = getelementptr i8, ptr addrspace(2) %base, i8 1
+  ret ptr addrspace(2) %gep
+}
+
+;; The same is true for pointers with external state: no new inttoptr
+define ptr addrspace(3) @test_null_base_external() {
+; CHECK-LABEL: define ptr addrspace(3) @test_null_base_external() {
+; CHECK-NEXT:    ret ptr addrspace(3) getelementptr (i8, ptr addrspace(3) null, i8 -2)
+;
+  %gep = getelementptr i8, ptr addrspace(3) null, i8 -2
+  ret ptr addrspace(3) %gep
+}
+
+define ptr addrspace(3) @test_inttoptr_base_external() {
+; CHECK-LABEL: define ptr addrspace(3) @test_inttoptr_base_external() {
+; CHECK-NEXT:    ret ptr addrspace(3) getelementptr (i8, ptr addrspace(3) inttoptr (i16 -1 to ptr addrspace(3)), i8 1)
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arichardson wrote:

I'm not sure this really matters for CHERI, we could also emit the `inttoptr (i16 -256 to ptr addrspace(1))` directly, but maybe it's cleaner to not attempt to perform any inttoptr based transforms?

https://github.com/llvm/llvm-project/pull/159959