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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@85341 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Bill Wendling 2009-10-27 23:30:07 +00:00
parent 1239c9656b
commit c872e9c07d
1 changed files with 35 additions and 0 deletions
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35
lib/Target/README.txt
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@ -1633,3 +1633,38 @@ This can be generalized for other forms:
b = (b & ~0x80) | (a & 0x40) << 1;
//===---------------------------------------------------------------------===//
These two functions produce different code. They shouldn't:
#include <stdint.h>
uint8_t p1(uint8_t b, uint8_t a) {
b = (b & ~0xc0) | (a & 0xc0);
return (b);
}
uint8_t p2(uint8_t b, uint8_t a) {
b = (b & ~0x40) | (a & 0x40);
b = (b & ~0x80) | (a & 0x80);
return (b);
}
define zeroext i8 @p1(i8 zeroext %b, i8 zeroext %a) nounwind readnone ssp {
entry:
%0 = and i8 %b, 63 ; <i8> [#uses=1]
%1 = and i8 %a, -64 ; <i8> [#uses=1]
%2 = or i8 %1, %0 ; <i8> [#uses=1]
ret i8 %2
}
define zeroext i8 @p2(i8 zeroext %b, i8 zeroext %a) nounwind readnone ssp {
entry:
%0 = and i8 %b, 63 ; <i8> [#uses=1]
%.masked = and i8 %a, 64 ; <i8> [#uses=1]
%1 = and i8 %a, -128 ; <i8> [#uses=1]
%2 = or i8 %1, %0 ; <i8> [#uses=1]
%3 = or i8 %2, %.masked ; <i8> [#uses=1]
ret i8 %3
}
//===---------------------------------------------------------------------===//