Add an ugly note.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@50029 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/X86/README.txt b/lib/Target/X86/README.txt
index 56dc29c2f2329ae792940c0055619dc70d29de3f..fcbae96bee01112350bd9497f2b84fed52f64b28 100644 (file)
--- a/lib/Target/X86/README.txt
+++ b/lib/Target/X86/README.txt
@@ -1656,3 +1656,38 @@ extending to the fall through). The register pressure in the loop isn't high
 enough to warrant the spill.
 
 Also check why xmm7 is not used at all in the function.
+
+//===---------------------------------------------------------------------===//
+
+Legalize loses track of the fact that bools are always zero extended when in
+memory.  This causes us to compile abort_gzip (from 164.gzip) from:
+
+target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
+target triple = "i386-apple-darwin8"
+@in_exit.4870.b = internal global i1 false             ; <i1*> [#uses=2]
+define fastcc void @abort_gzip() noreturn nounwind  {
+entry:
+       %tmp.b.i = load i1* @in_exit.4870.b             ; <i1> [#uses=1]
+       br i1 %tmp.b.i, label %bb.i, label %bb4.i
+bb.i:          ; preds = %entry
+       tail call void @exit( i32 1 ) noreturn nounwind 
+       unreachable
+bb4.i:         ; preds = %entry
+       store i1 true, i1* @in_exit.4870.b
+       tail call void @exit( i32 1 ) noreturn nounwind 
+       unreachable
+}
+declare void @exit(i32) noreturn nounwind 
+
+into:
+
+_abort_gzip:
+       subl    $12, %esp
+       movb    _in_exit.4870.b, %al
+       notb    %al
+       testb   $1, %al
+       jne     LBB1_2  ## bb4.i
+LBB1_1:        ## bb.i
+  ...
+
+//===---------------------------------------------------------------------===//