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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@30559 91177308-0d34-0410-b5e6-96231b3b80d8
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Chris Lattner 2006-09-21 06:14:54 +00:00
parent 111c228241
commit b13f83eb23
1 changed files with 0 additions and 35 deletions
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35
lib/Target/X86/README.txt
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@ -642,41 +642,6 @@ sequence)?
//===---------------------------------------------------------------------===// //===---------------------------------------------------------------------===//
Compile:
int %test(ulong *%tmp) {
%tmp = load ulong* %tmp ; <ulong> [#uses=1]
%tmp.mask = shr ulong %tmp, ubyte 50 ; <ulong> [#uses=1]
%tmp.mask = cast ulong %tmp.mask to ubyte
%tmp2 = and ubyte %tmp.mask, 3 ; <ubyte> [#uses=1]
%tmp2 = cast ubyte %tmp2 to int ; <int> [#uses=1]
ret int %tmp2
}
to:
_test:
movl 4(%esp), %eax
movl 4(%eax), %eax
shrl $18, %eax
andl $3, %eax
ret
instead of:
_test:
movl 4(%esp), %eax
movl 4(%eax), %eax
shrl $18, %eax
# TRUNCATE movb %al, %al
andb $3, %al
movzbl %al, %eax
ret
This saves a movzbl, and saves a truncate if it doesn't get coallesced right.
This is a simple DAGCombine to propagate the zext through the and.
//===---------------------------------------------------------------------===//
GCC's ix86_expand_int_movcc function (in i386.c) has a ton of interesting GCC's ix86_expand_int_movcc function (in i386.c) has a ton of interesting
simplifications for integer "x cmp y ? a : b". For example, instead of: simplifications for integer "x cmp y ? a : b". For example, instead of: