diff options
Diffstat (limited to 'lib/Target/README.txt')
| -rw-r--r-- | lib/Target/README.txt | 48 |
1 files changed, 3 insertions, 45 deletions
diff --git a/lib/Target/README.txt b/lib/Target/README.txt index a6e05fa..69da35f 100644 --- a/lib/Target/README.txt +++ b/lib/Target/README.txt @@ -282,19 +282,6 @@ this requires TBAA. //===---------------------------------------------------------------------===// -This should be optimized to one 'and' and one 'or', from PR4216: - -define i32 @test_bitfield(i32 %bf.prev.low) nounwind ssp { -entry: - %bf.prev.lo.cleared10 = or i32 %bf.prev.low, 32962 ; <i32> [#uses=1] - %0 = and i32 %bf.prev.low, -65536 ; <i32> [#uses=1] - %1 = and i32 %bf.prev.lo.cleared10, 40186 ; <i32> [#uses=1] - %2 = or i32 %1, %0 ; <i32> [#uses=1] - ret i32 %2 -} - -//===---------------------------------------------------------------------===// - This isn't recognized as bswap by instcombine (yes, it really is bswap): unsigned long reverse(unsigned v) { @@ -1661,38 +1648,9 @@ would delete the or instruction for us. //===---------------------------------------------------------------------===// -FunctionAttrs is not marking this function as readnone (just readonly): -$ clang t.c -emit-llvm -S -o - -O0 | opt -mem2reg -S -functionattrs - -int t(int a, int b, int c) { - int *p; - if (a) - p = &a; - else - p = &c; - return *p; -} - -This is because we codegen this to: - -define i32 @t(i32 %a, i32 %b, i32 %c) nounwind readonly ssp { -entry: - %a.addr = alloca i32 ; <i32*> [#uses=3] - %c.addr = alloca i32 ; <i32*> [#uses=2] -... - -if.end: - %p.0 = phi i32* [ %a.addr, %if.then ], [ %c.addr, %if.else ] - %tmp2 = load i32* %p.0 ; <i32> [#uses=1] - ret i32 %tmp2 -} - -And functionattrs doesn't realize that the p.0 load points to function local -memory. - -Also, functionattrs doesn't know about memcpy/memset. This function should be -marked readnone, since it only twiddles local memory, but functionattrs doesn't -handle memset/memcpy/memmove aggressively: +functionattrs doesn't know much about memcpy/memset. This function should be +marked readnone rather than readonly, since it only twiddles local memory, but +functionattrs doesn't handle memset/memcpy/memmove aggressively: struct X { int *p; int *q; }; int foo() { |
