Selectively invert ICMP operands for better address optimization

tests_lit/llvm2ice_tests/address-mode-opt.ll

 ; This file checks support for address mode optimization.
 
 ; RUN: %p2i --filetype=obj --disassemble -i %s --args -O2 \
 ; RUN:   -allow-externally-defined-symbols | FileCheck %s
 ; RUN: %p2i --filetype=obj --disassemble -i %s --args -O2 -mattr=sse4.1 \
 ; RUN:   -allow-externally-defined-symbols | FileCheck --check-prefix=SSE41 %s
 
 define internal float @load_arg_plus_200000(float* %arg) {
 entry:
   %arg.int = ptrtoint float* %arg to i32
@@ skipping 169 matching lines @@
   %arg.int = ptrtoint float* %arg to i32
   %shl1 = shl i32 %arg.int, 2
   %addr.int = or i32 -1, %shl1
   %addr.ptr = inttoptr i32 %addr.int to float*
   %addr.load = load float, float* %addr.ptr, align 4
   ret float %addr.load
 ; CHECK-LABEL: or_add_boundary_check_2
 ; CHECK: or
 ; CHECK-NOT: movss xmm{{[0-9]+}},DWORD PTR [{{e..}}*4+0xFFFF]
 }
+
+define internal void @invert_icmp(i32* %arg1, i32* %arg2) {
+entry:
+  %addr.other = load i32, i32* %arg2, align 1
+  br label %foo
+foo:

[Jim Stichnoth, 2016/07/08 11:45:46]

I would name this something like "next" instead of "foo", just to make it read a
bit more serious.

+  %addr.load = load i32, i32* %arg1, align 1
+  %cond = icmp slt i32 %addr.load, %addr.other
+  br i1 %cond, label %if.then, label %if.else
+if.then:
+  ret void
+if.else:
+  ret void
+; CHECK-LABEL: invert_icmp
+; CHECK: cmp {{e..}},DWORD PTR [{{e..}}]
+; CHECK: jle
+}