[x86] Teach the new vector shuffle lowering about the zero masking

[oota-llvm.git] / lib / Target / README.txt

diff --git a/lib/Target/README.txt b/lib/Target/README.txt
index 3c21ddae80ca69e94af98cdc88192d3b046b22fe..bf8d465d0aeebe9db2b1a2e5375fef188fa8853c 100644 (file)
--- a/lib/Target/README.txt
+++ b/lib/Target/README.txt
@@ -2,22 +2,6 @@ Target Independent Opportunities:
 
 //===---------------------------------------------------------------------===//
 
 
 //===---------------------------------------------------------------------===//
 

-With the recent changes to make the implicit def/use set explicit in
-machineinstrs, we should change the target descriptions for 'call' instructions
-so that the .td files don't list all the call-clobbered registers as implicit
-defs.  Instead, these should be added by the code generator (e.g. on the dag).
-
-This has a number of uses:
-
-1. PPC32/64 and X86 32/64 can avoid having multiple copies of call instructions
-   for their different impdef sets.
-2. Targets with multiple calling convs (e.g. x86) which have different clobber
-   sets don't need copies of call instructions.
-3. 'Interprocedural register allocation' can be done to reduce the clobber sets
-   of calls.
-
-//===---------------------------------------------------------------------===//
-

 We should recognized various "overflow detection" idioms and translate them into
 llvm.uadd.with.overflow and similar intrinsics.  Here is a multiply idiom:
 
 We should recognized various "overflow detection" idioms and translate them into
 llvm.uadd.with.overflow and similar intrinsics.  Here is a multiply idiom:
 


@@ -109,44 +93,6 @@ This requires reassociating to forms of expressions that are already available,
 something that reassoc doesn't think about yet.
 
 
 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:
 //===---------------------------------------------------------------------===//
 
 These two functions should generate the same code on big-endian systems:


@@ -168,7 +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.
 
 to the type size. It works but can be overly conservative as the alignment of
 specific vector types are target dependent.
 


@@ -278,22 +224,7 @@ unsigned countbits_slow(unsigned v) {
     c += v & 1;
   return c;
 }
     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++)
 unsigned int popcount(unsigned int input) {
   unsigned int count = 0;
   for (unsigned int i =  0; i < 4 * 8; i++)


@@ -980,6 +911,12 @@ optimized with "clang -emit-llvm-bc | opt -std-compile-opts".
 
 //===---------------------------------------------------------------------===//
 
 
 //===---------------------------------------------------------------------===//
 

+unsigned f(unsigned x) { return ((x & 7) + 1) & 15; }
+The & 15 part should be optimized away, it doesn't change the result. Currently
+not optimized with "clang -emit-llvm-bc | opt -std-compile-opts".
+
+//===---------------------------------------------------------------------===//
+

 This was noticed in the entryblock for grokdeclarator in 403.gcc:
 
         %tmp = icmp eq i32 %decl_context, 4          
 This was noticed in the entryblock for grokdeclarator in 403.gcc:
 
         %tmp = icmp eq i32 %decl_context, 4          


@@ -1188,7 +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]
 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
 
 [PRE OF READONLY CALL]
 loadpre5.c


@@ -2377,8 +2314,3 @@ unsigned foo(unsigned x, unsigned y) { return x > y && x != 0; }
 should fold to x > y.
 
 //===---------------------------------------------------------------------===//
 should fold to x > y.
 
 //===---------------------------------------------------------------------===//

-
-int f(double x) { return __builtin_fabs(x) < 0.0; }
-should fold to false.
-
-//===---------------------------------------------------------------------===//