Thumb2 assembly parsing and encoding for REV16/REVSH.

[oota-llvm.git] / lib / Target / README.txt

diff --git a/lib/Target/README.txt b/lib/Target/README.txt
index 4e382e8f8ec1aa49dbfe5150e98918857a0e3b7d..1f69ffb09c0a4a04298f9e84b91acd2b3c06b1ec 100644 (file)
--- a/lib/Target/README.txt
+++ b/lib/Target/README.txt
@@ -1762,7 +1762,6 @@ case it choses instead to keep the max operation obvious.
 
 //===---------------------------------------------------------------------===//
 
-Switch lowering generates less than ideal code for the following switch:
 define void @a(i32 %x) nounwind {
 entry:
   switch i32 %x, label %if.end [
@@ -1783,19 +1782,15 @@ declare void @foo()
 Generated code on x86-64 (other platforms give similar results):
 a:
        cmpl    $5, %edi
-       ja      .LBB0_2
-       movl    %edi, %eax
-       movl    $47, %ecx
-       btq     %rax, %rcx
-       jb      .LBB0_3
+       ja      LBB2_2
+       cmpl    $4, %edi
+       jne     LBB2_3
 .LBB0_2:
        ret
 .LBB0_3:
        jmp     foo  # TAILCALL
 
-The movl+movl+btq+jb could be simplified to a cmpl+jne.
-
-Or, if we wanted to be really clever, we could simplify the whole thing to
+If we wanted to be really clever, we could simplify the whole thing to
 something like the following, which eliminates a branch:
        xorl    $1, %edi
        cmpl    $4, %edi
@@ -2353,3 +2348,13 @@ which can do this in a single operation (instruction or libcall).  It is
 probably best to do this in the code generator.
 
 //===---------------------------------------------------------------------===//
+
+unsigned foo(unsigned x, unsigned y) { return (x & y) == 0 || x == 0; }
+should fold to (x & y) == 0.
+
+//===---------------------------------------------------------------------===//
+
+unsigned foo(unsigned x, unsigned y) { return x > y && x != 0; }
+should fold to x > y.
+
+//===---------------------------------------------------------------------===//