diff options
| -rw-r--r-- | lib/Target/X86/README.txt | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/lib/Target/X86/README.txt b/lib/Target/X86/README.txt index 9f22bab55d..3ee32cce05 100644 --- a/lib/Target/X86/README.txt +++ b/lib/Target/X86/README.txt @@ -711,4 +711,26 @@ bool %test(ulong %x) { 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 + +//===---------------------------------------------------------------------===// |