[llvm-dev] How to constraint instructions reordering from patterns?
Dominique Torette via llvm-dev
llvm-dev at lists.llvm.org
Fri May 4 07:11:28 PDT 2018
Krzysztof,
Thanks for your interest to my questions.
In order to clarify the context, here is the C source file of my test case.
The 3 builtins initialize some stack pointers. They have to be executed before any other instruction.
extern float fdivfaddfmul_a(float a, float b, float c, float d);
volatile static float x1,x2,x3,x4;
void _start(void)
{
float res;
__builtin_clp_set_rspa(64);
__builtin_clp_set_rspb(64);
__builtin_clp_set_rspsu(8);
x1 = 1.0f;
x2 = 2.0f;
x3 = 3.0f;
x4 = 4.0f;
res = fdivfaddfmul_a(x1,x2,x3,x4);
}
-----Original Message-----
From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] On Behalf Of Krzysztof Parzyszek via llvm-dev
Sent: vendredi 4 mai 2018 15:42
To: llvm-dev at lists.llvm.org
Subject: Re: [llvm-dev] How to constraint instructions reordering from patterns?
The DAG dumping will try to print some of the nodes "inline" (i.e. where they are used) to make the output more readable, so the dump of the DAG may not strictly reflect the node ordering.
-Krzysztof
On 5/4/2018 8:18 AM, Dominique Torette via llvm-dev wrote:
> Here is a last example to illustrate my concern.
>
> The problem is about the lowering of node t13.
>
> Initial selection DAG: BB#0 '_start:entry'
>
> SelectionDAG has 44 nodes:
>
> t11: i16 = Constant<0>
>
> t0: ch = EntryToken
>
> t3: ch = llvm.clp.set.rspa t0,
> TargetConstant:i16<392>, Constant:i32<64>
>
> t5: ch = llvm.clp.set.rspb t3, TargetConstant:i16<393>,
> Constant:i32<64>
>
> t8: ch = llvm.clp.set.rspsu t5, TargetConstant:i16<394>,
> Constant:i32<8>
>
> t13: ch = store<Volatile ST4[@x1](tbaa=<0x3dbe418>)> t8,
> ConstantFP:f32<1.000000e+00>, GlobalAddress:i16<float* @x1> 0,
> undef:i16
>
> t16: ch = store<Volatile ST4[@x2](tbaa=<0x3dbe418>)> t13,
> ConstantFP:f32<2.000000e+00>, GlobalAddress:i16<float* @x2> 0,
> undef:i16
>
> t19: ch = store<Volatile ST4[@x3](tbaa=<0x3dbe418>)> t16,
> ConstantFP:f32<3.000000e+00>, GlobalAddress:i16<float* @x3> 0,
> undef:i16
>
> t22: ch = store<Volatile ST4[@x4](tbaa=<0x3dbe418>)> t19,
> ConstantFP:f32<4.000000e+00>, GlobalAddress:i16<float* @x4> 0,
> undef:i16
>
> t23: f32,ch = load<Volatile LD4[@x1](tbaa=<0x3dbe418>)> t22,
> GlobalAddress:i16<float* @x1> 0, undef:i16
>
> t24: f32,ch = load<Volatile LD4[@x2](tbaa=<0x3dbe418>)> t23:1,
> GlobalAddress:i16<float* @x2> 0, undef:i16
>
> t25: f32,ch = load<Volatile LD4[@x3](tbaa=<0x3dbe418>)> t24:1,
> GlobalAddress:i16<float* @x3> 0, undef:i16
>
> t26: f32,ch = load<Volatile LD4[@x4](tbaa=<0x3dbe418>)> t25:1,
> GlobalAddress:i16<float* @x4> 0, undef:i16
>
> t27: i16 = GlobalAddress<float (float, float, float, float)*
> @fdivfaddfmul_a> 0
>
> t29: ch,glue = callseq_start t26:1, TargetConstant:i16<4>
>
> t31: ch,glue = CLPISD::COPY_TO_CALLEE_A t29, t23,
> FrameIndex:i16<0>,
> t29:1
>
> t33: ch,glue = CLPISD::COPY_TO_CALLEE_A t31, t24,
> FrameIndex:i16<1>,
> t31:1
>
> t35: ch,glue = CLPISD::COPY_TO_CALLEE_A t33, t25,
> FrameIndex:i16<2>,
> t33:1
>
> t37: ch,glue = CLPISD::COPY_TO_CALLEE_A t35, t26,
> FrameIndex:i16<3>,
> t35:1
>
> t39: ch,glue = CLPISD::CALLSEQ t37, TargetGlobalAddress:i16<float
> (float, float, float, float)* @fdivfaddfmul_a> 0, t37:1
>
> t41: ch,glue = callseq_end t39, TargetConstant:i16<4>,
> TargetConstant:i16<0>, t39:1
>
> t42: f32,ch,glue = CLPISD::COPY_TO_CALLER_A t41, FrameIndex:i16<0>,
> t41:1
>
> t43: ch = CLPISD::RET_FLAG t42:1
>
> This node is first ‘combined’ into node t51 (bitcast of ConstantFP f32
> to Constant i32).
>
> Combining: t13: ch = store<Volatile ST4[@x1](tbaa=<0x3dbe418>)> t8,
> ConstantFP:f32<1.000000e+00>, GlobalAddress:i16<float* @x1> 0,
> undef:i16
>
> ... into: t51: ch = store<Volatile ST4[@x1](tbaa=<0x3dbe418>)> t8,
> Constant:i32<1065353216>, GlobalAddress:i16<float* @x1> 0, undef:i16
>
> An a new Constant:i32 node (t50) is created.
>
> /The question is: Where in the graph is created this node?/
>
> This node seems to be created before the EntryToken !!! Before the
> initialization of my Stack Pointer registers (RSPA,RSPB,RSPSU).
>
> Why isn’t it created between t8 and t51?
>
> t0: ch = EntryToken
>
> t3: ch = llvm.clp.set.rspa t0,
> TargetConstant:i16<392>, Constant:i32<64>
>
> t5: ch = llvm.clp.set.rspb t3, TargetConstant:i16<393>,
> Constant:i32<64>
>
> t8: ch = llvm.clp.set.rspsu t5, TargetConstant:i16<394>,
> Constant:i32<8>
>
> t51: ch = store<Volatile ST4[@x1](tbaa=<0x3dbe418>)> t8,
> Constant:i32<1065353216>, TargetGlobalAddress:i32<float* @x1> 0,
> undef:i16
>
> t49: ch = store<Volatile ST4[@x2](tbaa=<0x3dbe418>)> t51,
> Constant:i32<1073741824>, TargetGlobalAddress:i32<float* @x2> 0,
> undef:i16
>
> t47: ch = store<Volatile ST4[@x3](tbaa=<0x3dbe418>)> t49,
> Constant:i32<1077936128>, TargetGlobalAddress:i32<float* @x3> 0,
> undef:i16
>
> t45: ch = store<Volatile ST4[@x4](tbaa=<0x3dbe418>)> t47,
> Constant:i32<1082130432>, TargetGlobalAddress:i32<float* @x4> 0,
> undef:i16
>
> t23: f32,ch = load<Volatile LD4[@x1](tbaa=<0x3dbe418>)> t45,
> TargetGlobalAddress:i32<float* @x1> 0, undef:i16
>
> t24: f32,ch = load<Volatile LD4[@x2](tbaa=<0x3dbe418>)> t23:1,
> TargetGlobalAddress:i32<float* @x2> 0, undef:i16
>
> t25: f32,ch = load<Volatile LD4[@x3](tbaa=<0x3dbe418>)> t24:1,
> TargetGlobalAddress:i32<float* @x3> 0, undef:i16
>
> t26: f32,ch = load<Volatile LD4[@x4](tbaa=<0x3dbe418>)> t25:1,
> TargetGlobalAddress:i32<float* @x4> 0, undef:i16
>
> t29: ch,glue = callseq_start t26:1, TargetConstant:i16<4>
>
> t31: ch,glue = CLPISD::COPY_TO_CALLEE_A t29, t23,
> TargetFrameIndex:i16<0>, t29:1
>
> t33: ch,glue = CLPISD::COPY_TO_CALLEE_A t31, t24,
> TargetFrameIndex:i16<1>, t31:1
>
> t35: ch,glue = CLPISD::COPY_TO_CALLEE_A t33, t25,
> TargetFrameIndex:i16<2>, t33:1
>
> t37: ch,glue = CLPISD::COPY_TO_CALLEE_A t35, t26,
> TargetFrameIndex:i16<3>, t35:1
>
> t39: ch,glue = CLPISD::CALLSEQ t37, TargetGlobalAddress:i16<float
> (float, float, float, float)* @fdivfaddfmul_a> 0, t37:1
>
> t41: ch,glue = callseq_end t39, TargetConstant:i16<4>,
> TargetConstant:i16<0>, t39:1
>
> t42: f32,ch,glue = CLPISD::COPY_TO_CALLER_A t41,
> TargetFrameIndex:i16<0>, t41:1
>
> t43: ch = CLPISD::RET_FLAG t42:1
>
> ISEL: Starting pattern match on root node: t50: i32 =
> Constant<1065353216>
>
> Initial Opcode index to 415
>
> TypeSwitch[i32] from 416 to 432
>
> Morphed node: t50: i32 = MOVSUTO_A_iSLo TargetConstant:i32<1065353216>
>
> def: Pat<(f32 fpimm:$imm),
>
> (MOVSUTO_A_iSLo (bitcast_fpimm_to_i32
> f32:$imm))>;
>
> def: Pat<(i32 imm:$imm),
>
> (MOVSUTO_A_iSLo (trunc_imm i32:$imm))>;
>
> ===== Instruction selection ends:
>
> Selected selection DAG: BB#0 '_start:entry'
>
> SelectionDAG has 42 nodes:
>
> t44: i32 = MOVSUTO_A_iSLo
> TargetConstant:i32<1082130432>
>
> t46: i32 = MOVSUTO_A_iSLo
> TargetConstant:i32<1077936128>
>
> t48: i32 = MOVSUTO_A_iSLo
> TargetConstant:i32<1073741824>
>
> t50: i32 = MOVSUTO_A_iSLo TargetConstant:i32<1065353216>
>
> t0: ch = EntryToken
>
> t3: ch = MOV_SU_iSSs_rspa
> TargetConstant:i32<64>, t0
>
> t5: ch = MOV_SU_iSSs_rspb
> TargetConstant:i32<64>, t3
>
> t8: ch = MOV_SU_iSSs_rspsu TargetConstant:i32<8>,
> t5
>
> t51: ch = MOV_A_or t50,
> TargetGlobalAddress:i32<float* @x1> 0, t8
>
> t49: ch = MOV_A_or t48,
> TargetGlobalAddress:i32<float* @x2> 0, t51
>
> t47: ch = MOV_A_or t46, TargetGlobalAddress:i32<float*
> @x3> 0, t49
>
> t45: ch = MOV_A_or t44, TargetGlobalAddress:i32<float*
> @x4> 0, t47
>
> t23: f32,ch = MOV_A_ro TargetGlobalAddress:i32<float* @x1> 0, t45
>
> t24: f32,ch = MOV_A_ro TargetGlobalAddress:i32<float* @x2> 0,
> t23:1
>
> t25: f32,ch = MOV_A_ro TargetGlobalAddress:i32<float* @x3> 0,
> t24:1
>
> t26: f32,ch = MOV_A_ro TargetGlobalAddress:i32<float* @x4> 0,
> t25:1
>
> t29: ch,glue = CALLSEQ_START TargetConstant:i16<4>, t26:1
>
> t31: ch,glue = COPY_TO_CALLEE_A_FROM_GLOBAL
> TargetGlobalAddress:i32<float* @x1> 0, TargetFrameIndex:i16<0>, t29,
> t29:1
>
> t33: ch,glue = COPY_TO_CALLEE_A_FROM_GLOBAL
> TargetGlobalAddress:i32<float* @x2> 0, TargetFrameIndex:i16<1>, t31,
> t31:1
>
> t35: ch,glue = COPY_TO_CALLEE_A_FROM_GLOBAL
> TargetGlobalAddress:i32<float* @x3> 0, TargetFrameIndex:i16<2>, t33,
> t33:1
>
> t37: ch,glue = COPY_TO_CALLEE_A_FROM_GLOBAL
> TargetGlobalAddress:i32<float* @x4> 0, TargetFrameIndex:i16<3>, t35,
> t35:1
>
> t39: ch,glue = CALLSEQ TargetGlobalAddress:i16<float (float, float,
> float, float)* @fdivfaddfmul_a> 0, t37, t37:1
>
> t41: ch,glue = CALLSEQ_END TargetConstant:i16<4>,
> TargetConstant:i16<0>, t39, t39:1
>
> t42: f32,ch,glue = COPY_TO_CALLER_A TargetFrameIndex:i16<0>, t41,
> t41:1
>
> t43: ch = RET_FLAG t42:1
>
> *From:*llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] *On Behalf Of
> *Dominique Torette via llvm-dev
> *Sent:* vendredi 4 mai 2018 12:43
> *To:* llvm-dev at lists.llvm.org
> *Subject:* [llvm-dev] How to constraint instructions reordering from
> patterns?
>
> Hi,
>
> Is there a kind of scope mechanism in the instruction lowering pattern
> language in order to control where instructions are inserted or how
> they are later reordered during the SelectionDiag linearization?
>
> I know the glue chain that stick instructions together. But such
> mechanism in not provided in instruction lowering pattern.
>
> I’m facing many situations where some patterns are lowered into valid
> sequences of consecutive SDNodes/Instructions.
>
> Such sequences have no glue, so later during Instruction
> Scheduling/SelectionDiag linearization the instructions are moved out
> of valid context.
>
> Is there some Instruction flags or others features that could delimit
> the reordering could cross some limit?
>
> TIA, Dominique Torette
>
> http://www.spacebel.be/wp-content/uploads/2018/02/image-sign-sbp30y-1.
> jpg
>
> *Dominique Torette*
> System Architect
> Rue des Chasseurs Ardennais - Liège Science Park - B-4031 Angleur
> Tel: +32 (0) 4 361 81 11 - Fax: +32 (0) 4 361 81 20 www.spacebel.be
> <http://www.spacebel.be/>
>
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