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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@30921 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2006-10-12 22:01:26 +00:00
parent 26d2990e03
commit 15bdc96c5b
1 changed files with 27 additions and 0 deletions
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27
lib/Target/X86/README.txt
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@ -734,3 +734,30 @@ _foo:
ret
//===---------------------------------------------------------------------===//
Consider the expansion of:
uint %test3(uint %X) {
%tmp1 = rem uint %X, 255
ret uint %tmp1
}
Currently it compiles to:
...
movl $2155905153, %ecx
movl 8(%esp), %esi
movl %esi, %eax
mull %ecx
...
This could be "reassociated" into:
movl $2155905153, %eax
movl 8(%esp), %ecx
mull %ecx
to avoid the copy. In fact, the existing two-address stuff would do this
except that mul isn't a commutative 2-addr instruction. I guess this has
to be done at isel time based on the #uses to mul?