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of some code. This exposes the implicit load from the stubs to the DAG, allowing them to be optimized by the dag combiner. It also moves darwin specific stuff out of the isel into the legalizer, and allows more to be moved to the .td file. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@24397 91177308-0d34-0410-b5e6-96231b3b80d8
225 lines
6.1 KiB
Plaintext
225 lines
6.1 KiB
Plaintext
TODO:
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* gpr0 allocation
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* implement do-loop -> bdnz transform
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* implement powerpc-64 for darwin
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* use stfiwx in float->int
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* be able to combine sequences like the following into 2 instructions:
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lis r2, ha16(l2__ZTV4Cell)
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la r2, lo16(l2__ZTV4Cell)(r2)
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addi r2, r2, 8
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* Teach LLVM how to codegen this:
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unsigned short foo(float a) { return a; }
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as:
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_foo:
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fctiwz f0,f1
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stfd f0,-8(r1)
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lhz r3,-2(r1)
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blr
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not:
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_foo:
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fctiwz f0, f1
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stfd f0, -8(r1)
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lwz r2, -4(r1)
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rlwinm r3, r2, 0, 16, 31
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blr
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and:
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extern int X, Y; int* test(int C) { return C? &X : &Y; }
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as one load when using --enable-pic.
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* Support 'update' load/store instructions. These are cracked on the G5, but
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are still a codesize win.
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* should hint to the branch select pass that it doesn't need to print the
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second unconditional branch, so we don't end up with things like:
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b .LBBl42__2E_expand_function_8_674 ; loopentry.24
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b .LBBl42__2E_expand_function_8_42 ; NewDefault
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b .LBBl42__2E_expand_function_8_42 ; NewDefault
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===-------------------------------------------------------------------------===
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* Codegen this:
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void test2(int X) {
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if (X == 0x12345678) bar();
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}
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as:
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xoris r0,r3,0x1234
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cmpwi cr0,r0,0x5678
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beq cr0,L6
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not:
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lis r2, 4660
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ori r2, r2, 22136
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cmpw cr0, r3, r2
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bne .LBB_test2_2
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===-------------------------------------------------------------------------===
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Lump the constant pool for each function into ONE pic object, and reference
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pieces of it as offsets from the start. For functions like this (contrived
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to have lots of constants obviously):
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double X(double Y) { return (Y*1.23 + 4.512)*2.34 + 14.38; }
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We generate:
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_X:
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lis r2, ha16(.CPI_X_0)
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lfd f0, lo16(.CPI_X_0)(r2)
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lis r2, ha16(.CPI_X_1)
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lfd f2, lo16(.CPI_X_1)(r2)
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fmadd f0, f1, f0, f2
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lis r2, ha16(.CPI_X_2)
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lfd f1, lo16(.CPI_X_2)(r2)
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lis r2, ha16(.CPI_X_3)
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lfd f2, lo16(.CPI_X_3)(r2)
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fmadd f1, f0, f1, f2
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blr
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It would be better to materialize .CPI_X into a register, then use immediates
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off of the register to avoid the lis's. This is even more important in PIC
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mode.
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===-------------------------------------------------------------------------===
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Implement Newton-Rhapson method for improving estimate instructions to the
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correct accuracy, and implementing divide as multiply by reciprocal when it has
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more than one use. Itanium will want this too.
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===-------------------------------------------------------------------------===
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int foo(int a, int b) { return a == b ? 16 : 0; }
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_foo:
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cmpw cr7, r3, r4
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mfcr r2
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rlwinm r2, r2, 31, 31, 31
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slwi r3, r2, 4
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blr
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If we exposed the srl & mask ops after the MFCR that we are doing to select
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the correct CR bit, then we could fold the slwi into the rlwinm before it.
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===-------------------------------------------------------------------------===
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#define ARRAY_LENGTH 16
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union bitfield {
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struct {
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#ifndef __ppc__
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unsigned int field0 : 6;
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unsigned int field1 : 6;
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unsigned int field2 : 6;
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unsigned int field3 : 6;
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unsigned int field4 : 3;
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unsigned int field5 : 4;
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unsigned int field6 : 1;
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#else
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unsigned int field6 : 1;
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unsigned int field5 : 4;
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unsigned int field4 : 3;
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unsigned int field3 : 6;
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unsigned int field2 : 6;
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unsigned int field1 : 6;
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unsigned int field0 : 6;
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#endif
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} bitfields, bits;
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unsigned int u32All;
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signed int i32All;
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float f32All;
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};
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typedef struct program_t {
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union bitfield array[ARRAY_LENGTH];
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int size;
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int loaded;
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} program;
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void AdjustBitfields(program* prog, unsigned int fmt1)
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{
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unsigned int shift = 0;
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unsigned int texCount = 0;
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unsigned int i;
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for (i = 0; i < 8; i++)
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{
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prog->array[i].bitfields.field0 = texCount;
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prog->array[i].bitfields.field1 = texCount + 1;
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prog->array[i].bitfields.field2 = texCount + 2;
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prog->array[i].bitfields.field3 = texCount + 3;
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texCount += (fmt1 >> shift) & 0x7;
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shift += 3;
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}
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}
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In the loop above, the bitfield adds get generated as
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(add (shl bitfield, C1), (shl C2, C1)) where C2 is 1, 2 or 3.
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Since the input to the (or and, and) is an (add) rather than a (shl), the shift
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doesn't get folded into the rlwimi instruction. We should ideally see through
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things like this, rather than forcing llvm to generate the equivalent
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(shl (add bitfield, C2), C1) with some kind of mask.
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===-------------------------------------------------------------------------===
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Compile this (standard bitfield insert of a constant):
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void %test(uint* %tmp1) {
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%tmp2 = load uint* %tmp1 ; <uint> [#uses=1]
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%tmp5 = or uint %tmp2, 257949696 ; <uint> [#uses=1]
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%tmp6 = and uint %tmp5, 4018143231 ; <uint> [#uses=1]
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store uint %tmp6, uint* %tmp1
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ret void
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}
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to:
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_test:
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lwz r0,0(r3)
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li r2,123
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rlwimi r0,r2,21,3,10
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stw r0,0(r3)
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blr
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instead of:
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_test:
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lis r2, -4225
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lwz r4, 0(r3)
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ori r2, r2, 65535
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oris r4, r4, 3936
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and r2, r4, r2
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stw r2, 0(r3)
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blr
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===-------------------------------------------------------------------------===
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Compile this:
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int %f1(int %a, int %b) {
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%tmp.1 = and int %a, 15 ; <int> [#uses=1]
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%tmp.3 = and int %b, 240 ; <int> [#uses=1]
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%tmp.4 = or int %tmp.3, %tmp.1 ; <int> [#uses=1]
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ret int %tmp.4
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}
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without a copy. We make this currently:
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_f1:
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rlwinm r2, r4, 0, 24, 27
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rlwimi r2, r3, 0, 28, 31
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or r3, r2, r2
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blr
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The two-addr pass or RA needs to learn when it is profitable to commute an
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instruction to avoid a copy AFTER the 2-addr instruction. The 2-addr pass
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currently only commutes to avoid inserting a copy BEFORE the two addr instr.
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