1 files changed, 66 insertions, 5 deletions
diff --git a/lib/Target/X86/README.txt b/lib/Target/X86/README.txt
index aa7bb3d978..d4545a6fcf 100644
--- a/lib/Target/X86/README.txt
+++ b/lib/Target/X86/README.txt
@@ -227,11 +227,6 @@ lambda, siod, optimizer-eval, ackermann, hash2, nestedloop, strcat, and Treesor.
 
 //===---------------------------------------------------------------------===//
 
-Teach the coalescer to coalesce vregs of different register classes. e.g. FR32 /
-FR64 to VR128.
-
-//===---------------------------------------------------------------------===//
-
 Adding to the list of cmp / test poor codegen issues:
 
 int test(__m128 *A, __m128 *B) {
@@ -1868,3 +1863,69 @@ carried over to machine instructions. Asm printer (or JIT) can use this
 information to add the "lock" prefix.
 
 //===---------------------------------------------------------------------===//
+
+_Bool bar(int *x) { return *x & 1; }
+
+define zeroext i1 @bar(i32* nocapture %x) nounwind readonly {
+entry:
+  %tmp1 = load i32* %x                            ; <i32> [#uses=1]
+  %and = and i32 %tmp1, 1                         ; <i32> [#uses=1]
+  %tobool = icmp ne i32 %and, 0                   ; <i1> [#uses=1]
+  ret i1 %tobool
+}
+
+bar:                                                        # @bar
+# BB#0:                                                     # %entry
+	movl	4(%esp), %eax
+	movb	(%eax), %al
+	andb	$1, %al
+	movzbl	%al, %eax
+	ret
+
+Missed optimization: should be movl+andl.
+
+//===---------------------------------------------------------------------===//
+
+Consider the following two functions compiled with clang:
+_Bool foo(int *x) { return !(*x & 4); }
+unsigned bar(int *x) { return !(*x & 4); }
+
+foo:
+	movl	4(%esp), %eax
+	testb	$4, (%eax)
+	sete	%al
+	movzbl	%al, %eax
+	ret
+
+bar:
+	movl	4(%esp), %eax
+	movl	(%eax), %eax
+	shrl	$2, %eax
+	andl	$1, %eax
+	xorl	$1, %eax
+	ret
+
+The second function generates more code even though the two functions are
+are functionally identical.
+
+//===---------------------------------------------------------------------===//
+
+Take the following C code:
+int x(int y) { return (y & 63) << 14; }
+
+Code produced by gcc:
+	andl	$63, %edi
+	sall	$14, %edi
+	movl	%edi, %eax
+	ret
+
+Code produced by clang:
+	shll	$14, %edi
+	movl	%edi, %eax
+	andl	$1032192, %eax
+	ret
+
+The code produced by gcc is 3 bytes shorter.  This sort of construct often
+shows up with bitfields.
+
+//===---------------------------------------------------------------------===//