X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FTarget%2FREADME.txt;h=bf8d465d0aeebe9db2b1a2e5375fef188fa8853c;hb=80b9e006aa9baa9857db97113742d1101a57b85d;hp=cbfa4cf35ba2f35ebf50ea79883ce7ad403fc5c7;hpb=d52998a8155e2c45d131e2dbfb97c3fdcbb57435;p=oota-llvm.git diff --git a/lib/Target/README.txt b/lib/Target/README.txt index cbfa4cf35ba..bf8d465d0ae 100644 --- a/lib/Target/README.txt +++ b/lib/Target/README.txt @@ -93,44 +93,6 @@ This requires reassociating to forms of expressions that are already available, something that reassoc doesn't think about yet. -//===---------------------------------------------------------------------===// - -This function: (derived from GCC PR19988) -double foo(double x, double y) { - return ((x + 0.1234 * y) * (x + -0.1234 * y)); -} - -compiles to: -_foo: - movapd %xmm1, %xmm2 - mulsd LCPI1_1(%rip), %xmm1 - mulsd LCPI1_0(%rip), %xmm2 - addsd %xmm0, %xmm1 - addsd %xmm0, %xmm2 - movapd %xmm1, %xmm0 - mulsd %xmm2, %xmm0 - ret - -Reassociate should be able to turn it into: - -double foo(double x, double y) { - return ((x + 0.1234 * y) * (x - 0.1234 * y)); -} - -Which allows the multiply by constant to be CSE'd, producing: - -_foo: - mulsd LCPI1_0(%rip), %xmm1 - movapd %xmm1, %xmm2 - addsd %xmm0, %xmm2 - subsd %xmm1, %xmm0 - mulsd %xmm2, %xmm0 - ret - -This doesn't need -ffast-math support at all. This is particularly bad because -the llvm-gcc frontend is canonicalizing the later into the former, but clang -doesn't have this problem. - //===---------------------------------------------------------------------===// These two functions should generate the same code on big-endian systems: @@ -152,7 +114,7 @@ stuff too. //===---------------------------------------------------------------------===// -For vector types, TargetData.cpp::getTypeInfo() returns alignment that is equal +For vector types, DataLayout.cpp::getTypeInfo() returns alignment that is equal to the type size. It works but can be overly conservative as the alignment of specific vector types are target dependent. @@ -262,22 +224,7 @@ unsigned countbits_slow(unsigned v) { c += v & 1; return c; } -unsigned countbits_fast(unsigned v){ - unsigned c; - for (c = 0; v; c++) - v &= v - 1; // clear the least significant bit set - return c; -} -BITBOARD = unsigned long long -int PopCnt(register BITBOARD a) { - register int c=0; - while(a) { - c++; - a &= a - 1; - } - return c; -} unsigned int popcount(unsigned int input) { unsigned int count = 0; for (unsigned int i = 0; i < 4 * 8; i++) @@ -1178,7 +1125,7 @@ There are many load PRE testcases in testsuite/gcc.dg/tree-ssa/loadpre* in the GCC testsuite, ones we don't get yet are (checked through loadpre25): [CRIT EDGE BREAKING] -loadpre3.c predcom-4.c +predcom-4.c [PRE OF READONLY CALL] loadpre5.c @@ -2367,8 +2314,3 @@ unsigned foo(unsigned x, unsigned y) { return x > y && x != 0; } should fold to x > y. //===---------------------------------------------------------------------===// - -int f(double x) { return __builtin_fabs(x) < 0.0; } -should fold to false. - -//===---------------------------------------------------------------------===//