[nfc] Add regression test for large offsets in X86 ISel

Author: wesleywiser

llvm/test/CodeGen/X86/dag-large-offset.ll

@@ -0,0 +1,46 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
+; RUN: llc < %s -mtriple=i386 --frame-pointer=all | FileCheck %s
+
+; ISel will try to fold pointer arithmetic into the address displacement. However, we don't
+; want to do that if the offset is very close to the expressible limit because the final frame
+; layout may push it over/under the limit.
+
+define i32 @foo(i1 %b) #0 {
+; CHECK-LABEL: foo:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    pushl %ebp
+; CHECK-NEXT:    .cfi_def_cfa_offset 8
+; CHECK-NEXT:    .cfi_offset %ebp, -8
+; CHECK-NEXT:    movl %esp, %ebp
+; CHECK-NEXT:    .cfi_def_cfa_register %ebp
+; CHECK-NEXT:    subl $8, %esp
+; CHECK-NEXT:    movl __stack_chk_guard, %eax
+; CHECK-NEXT:    movl %eax, -4(%ebp)
+; CHECK-NEXT:    testb $1, 8(%ebp)
+; CHECK-NEXT:    jne .LBB0_1
+; CHECK-NEXT:  # %bb.2: # %entry
+; CHECK-NEXT:    xorl %eax, %eax
+; CHECK-NEXT:    jmp .LBB0_3
+; CHECK-NEXT:  .LBB0_1:
+; CHECK-NEXT:    leal 2147483644(%ebp), %eax
+; CHECK-NEXT:  .LBB0_3: # %entry
+; CHECK-NEXT:    movl __stack_chk_guard, %ecx
+; CHECK-NEXT:    cmpl -4(%ebp), %ecx
+; CHECK-NEXT:    jne .LBB0_5
+; CHECK-NEXT:  # %bb.4: # %entry
+; CHECK-NEXT:    addl $8, %esp
+; CHECK-NEXT:    popl %ebp
+; CHECK-NEXT:    .cfi_def_cfa %esp, 4
+; CHECK-NEXT:    retl
+; CHECK-NEXT:  .LBB0_5: # %entry
+; CHECK-NEXT:    .cfi_def_cfa %ebp, 8
+; CHECK-NEXT:    calll __stack_chk_fail
+entry:
+  %a = alloca i8, align 1
+  %0 = ptrtoint ptr %a to i32
+  %sub = add i32 %0, -2147483647
+  %retval.0 = select i1 %b, i32 %sub, i32 0
+  ret i32 %retval.0
+}
+
+attributes #0 = { sspreq }