Target Independent Opportunities:
-===-------------------------------------------------------------------------===
+//===---------------------------------------------------------------------===//
+
+We should make the following changes to clean up MachineInstr:
+
+1. Add an Opcode field to TargetInstrDescriptor, so you can tell the opcode of
+ an instruction with just a TargetInstrDescriptor*.
+2. Remove the Opcode field from MachineInstr, replacing it with a
+ TargetInstrDescriptor*.
+3. Getting information about a machine instr then becomes:
+ MI->getInfo()->isTwoAddress()
+ instead of:
+ const TargetInstrInfo &TII = ...
+ TII.isTwoAddrInstr(MI->getOpcode())
+
+//===---------------------------------------------------------------------===//
+
+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.
+
+//===---------------------------------------------------------------------===//
FreeBench/mason contains code like this:
return v;
}
+Nor is this:
+
+ushort %bad(ushort %a) {
+entry:
+ %tmp = cast ushort %a to uint ; <uint> [#uses=1]
+ %tmp2 = shr uint %tmp, ubyte 8 ; <uint> [#uses=1]
+ %tmp2 = cast uint %tmp2 to ushort ; <ushort> [#uses=1]
+ %tmp5 = shl ushort %a, ubyte 8 ; <ushort> [#uses=1]
+ %tmp6 = or ushort %tmp2, %tmp5 ; <ushort> [#uses=1]
+ ret ushort %tmp6
+}
+
+unsigned short bad(unsigned short a) {
+ return ((a & 0xff00) >> 8 | (a & 0x00ff) << 8);
+}
+
//===---------------------------------------------------------------------===//
These should turn into single 16-bit (unaligned?) loads on little/big endian
}
//===---------------------------------------------------------------------===//
+
+-scalarrepl should promote this to be a vector scalar.
+
+ %struct..0anon = type { <4 x float> }
+implementation ; Functions:
+void %test1(<4 x float> %V, float* %P) {
+entry:
+ %u = alloca %struct..0anon, align 16 ; <%struct..0anon*> [#uses=2]
+ %tmp = getelementptr %struct..0anon* %u, int 0, uint 0 ; <<4 x float>*> [#uses=1]
+ store <4 x float> %V, <4 x float>* %tmp
+ %tmp1 = cast %struct..0anon* %u to [4 x float]* ; <[4 x float]*> [#uses=1]
+ %tmp = getelementptr [4 x float]* %tmp1, int 0, int 1 ; <float*> [#uses=1]
+ %tmp = load float* %tmp ; <float> [#uses=1]
+ %tmp3 = mul float %tmp, 2.000000e+00 ; <float> [#uses=1]
+ store float %tmp3, float* %P
+ ret void
+}
+
+//===---------------------------------------------------------------------===//
+
+-instcombine should handle this transform:
+ setcc (sdiv X / C1 ), C2
+when X, C1, and C2 are unsigned. Similarly for udiv and signed operands.
+
+Currently InstCombine avoids this transform but will do it when the signs of
+the operands and the sign of the divide match. See the FIXME in
+InstructionCombining.cpp in the visitSetCondInst method after the switch case
+for Instruction::UDiv (around line 4447) for more details.
+
+The SingleSource/Benchmarks/Shootout-C++/hash and hash2 tests have examples of
+this construct.
+
+//===---------------------------------------------------------------------===//
+
+Instcombine misses several of these cases (see the testcase in the patch):
+http://gcc.gnu.org/ml/gcc-patches/2006-10/msg01519.html
+
+//===---------------------------------------------------------------------===//
+
+viterbi speeds up *significantly* if the various "history" related copy loops
+are turned into memcpy calls at the source level. We need a "loops to memcpy"
+pass.
+
+//===---------------------------------------------------------------------===//
+
+-predsimplify should transform this:
+
+void bad(unsigned x)
+{
+ if (x > 4)
+ bar(12);
+ else if (x > 3)
+ bar(523);
+ else if (x > 2)
+ bar(36);
+ else if (x > 1)
+ bar(65);
+ else if (x > 0)
+ bar(45);
+ else
+ bar(367);
+}
+
+into:
+
+void good(unsigned x)
+{
+ if (x == 4)
+ bar(523);
+ else if (x == 3)
+ bar(36);
+ else if (x == 2)
+ bar(65);
+ else if (x == 1)
+ bar(45);
+ else if (x == 0)
+ bar(367);
+ else
+ bar(12);
+}
+
+to enable further optimizations.
+
+//===---------------------------------------------------------------------===//
projects / oota-llvm.git / blobdiff