[llvm-commits] CVS: llvm/lib/Target/X86/README.txt

[Chris Lattner]

Changes in directory llvm/lib/Target/X86:

README.txt updated: 1.140 -> 1.141
---
Log message:

ugly codegen


---
Diffs of the changes:  (+22 -0)

 README.txt |   22 ++++++++++++++++++++++
 1 files changed, 22 insertions(+)


Index: llvm/lib/Target/X86/README.txt
diff -u llvm/lib/Target/X86/README.txt:1.140 llvm/lib/Target/X86/README.txt:1.141
--- llvm/lib/Target/X86/README.txt:1.140	Fri Oct  6 03:21:07 2006
+++ llvm/lib/Target/X86/README.txt	Fri Oct  6 12:39:34 2006
@@ -711,4 +711,26 @@
 
 into x.h == 0
 
+//===---------------------------------------------------------------------===//
 
+We currently compile sign_extend_inreg into two shifts:
+
+long foo(long X) {
+  return (long)(signed char)X;
+}
+
+becomes:
+
+_foo:
+        movl 4(%esp), %eax
+        shll $24, %eax
+        sarl $24, %eax
+        ret
+
+This could be:
+
+_foo:
+        movsbl  4(%esp),%eax
+        ret
+
+//===---------------------------------------------------------------------===//