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[InlineSpiller] Relax re-materialization restriction for statepoint
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We should be careful to allow count of re-materialization of operands to be less
then number of physical registers.

STATEPOINT instruction has a variable number of operands and potentially very big.
So re-materialization for all operands is disabled at the moment if restrict-statepoint-remat is true.

The patch relaxes the re-materialization restriction for STATEPOINT instruction allowing it for
fixed operands. Specifically it is about call target.

Reviewers: reames
Reviewed By: reames
Subscribers: llvm-commits, qcolombet, hiraditya
Differential Revision: https://reviews.llvm.org/D75335
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Serguei Katkov committed Mar 2, 2020
1 parent 315f8a5 commit 496e0a9
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15 changes: 14 additions & 1 deletion llvm/lib/CodeGen/InlineSpiller.cpp
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Expand Up @@ -40,6 +40,7 @@
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/SlotIndexes.h"
#include "llvm/CodeGen/StackMaps.h"
#include "llvm/CodeGen/TargetInstrInfo.h"
#include "llvm/CodeGen/TargetOpcodes.h"
#include "llvm/CodeGen/TargetRegisterInfo.h"
Expand Down Expand Up @@ -536,7 +537,19 @@ bool InlineSpiller::canGuaranteeAssignmentAfterRemat(unsigned VReg,
// At the moment, we only handle this for STATEPOINTs since they're the only
// pseudo op where we've seen this. If we start seeing other instructions
// with the same problem, we need to revisit this.
return (MI.getOpcode() != TargetOpcode::STATEPOINT);
if (MI.getOpcode() != TargetOpcode::STATEPOINT)
return true;
// For STATEPOINTs we allow re-materialization for fixed arguments only hoping
// that number of physical registers is enough to cover all fixed arguments.
// If it is not true we need to revisit it.
for (unsigned Idx = StatepointOpers(&MI).getVarIdx(),
EndIdx = MI.getNumOperands();
Idx < EndIdx; ++Idx) {
MachineOperand &MO = MI.getOperand(Idx);
if (MO.isReg() && MO.getReg() == VReg)
return false;
}
return true;
}

/// reMaterializeFor - Attempt to rematerialize before MI instead of reloading.
Expand Down
132 changes: 132 additions & 0 deletions llvm/test/CodeGen/X86/statepoint-live-in-remat.ll
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@@ -0,0 +1,132 @@
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
; RUN: llc -code-model=large -verify-machineinstrs -O3 -restrict-statepoint-remat=true < %s | FileCheck %s
target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-apple-macosx10.11.0"

declare void @bar() #0

; This stresses our rematerialization handling.
; Target of statepoint is able to be re-materialized.
define void @test(i32 %a, i32 %b, i32 %c, i32 %d, i32 %e, i32 %f, i32 %g, i32 %h, i32 %i, i32 %j, i32 %k, i32 %l, i32 %m, i32 %n, i32 %o, i32 %p, i32 %q, i32 %r, i32 %s, i32 %t, i32 %u, i32 %v, i32 %w, i32 %x, i32 %y, i32 %z) gc "statepoint-example" {
; The code for this is terrible, check simply for correctness for the moment
; CHECK-LABEL: test:
; CHECK: ## %bb.0:
; CHECK-NEXT: pushq %rbp
; CHECK-NEXT: .cfi_def_cfa_offset 16
; CHECK-NEXT: pushq %r15
; CHECK-NEXT: .cfi_def_cfa_offset 24
; CHECK-NEXT: pushq %r14
; CHECK-NEXT: .cfi_def_cfa_offset 32
; CHECK-NEXT: pushq %r13
; CHECK-NEXT: .cfi_def_cfa_offset 40
; CHECK-NEXT: pushq %r12
; CHECK-NEXT: .cfi_def_cfa_offset 48
; CHECK-NEXT: pushq %rbx
; CHECK-NEXT: .cfi_def_cfa_offset 56
; CHECK-NEXT: subq $104, %rsp
; CHECK-NEXT: .cfi_def_cfa_offset 160
; CHECK-NEXT: .cfi_offset %rbx, -56
; CHECK-NEXT: .cfi_offset %r12, -48
; CHECK-NEXT: .cfi_offset %r13, -40
; CHECK-NEXT: .cfi_offset %r14, -32
; CHECK-NEXT: .cfi_offset %r15, -24
; CHECK-NEXT: .cfi_offset %rbp, -16
; CHECK-NEXT: movl %r9d, %r14d
; CHECK-NEXT: movl %r8d, %r15d
; CHECK-NEXT: movl %ecx, %r12d
; CHECK-NEXT: movl %edx, %r13d
; CHECK-NEXT: movl %esi, %ebx
; CHECK-NEXT: movl %edi, %ebp
; CHECK-NEXT: movabsq $_bar, %rax
; CHECK-NEXT: callq *%rax
; CHECK-NEXT: movl %ebp, %eax
; CHECK-NEXT: movq %rax, {{[-0-9]+}}(%r{{[sb]}}p) ## 8-byte Spill
; CHECK-NEXT: movl %ebx, %eax
; CHECK-NEXT: movq %rax, {{[-0-9]+}}(%r{{[sb]}}p) ## 8-byte Spill
; CHECK-NEXT: movl %r13d, %eax
; CHECK-NEXT: movq %rax, {{[-0-9]+}}(%r{{[sb]}}p) ## 8-byte Spill
; CHECK-NEXT: movl %r12d, %eax
; CHECK-NEXT: movq %rax, {{[-0-9]+}}(%r{{[sb]}}p) ## 8-byte Spill
; CHECK-NEXT: movl %r15d, %eax
; CHECK-NEXT: movq %rax, {{[-0-9]+}}(%r{{[sb]}}p) ## 8-byte Spill
; CHECK-NEXT: movl %r14d, %eax
; CHECK-NEXT: movq %rax, {{[-0-9]+}}(%r{{[sb]}}p) ## 8-byte Spill
; CHECK-NEXT: movl {{[0-9]+}}(%rsp), %eax
; CHECK-NEXT: movq %rax, {{[-0-9]+}}(%r{{[sb]}}p) ## 8-byte Spill
; CHECK-NEXT: movl {{[0-9]+}}(%rsp), %eax
; CHECK-NEXT: movq %rax, {{[-0-9]+}}(%r{{[sb]}}p) ## 8-byte Spill
; CHECK-NEXT: movl {{[0-9]+}}(%rsp), %eax
; CHECK-NEXT: movq %rax, {{[-0-9]+}}(%r{{[sb]}}p) ## 8-byte Spill
; CHECK-NEXT: movl {{[0-9]+}}(%rsp), %eax
; CHECK-NEXT: movq %rax, {{[-0-9]+}}(%r{{[sb]}}p) ## 8-byte Spill
; CHECK-NEXT: movl {{[0-9]+}}(%rsp), %eax
; CHECK-NEXT: movq %rax, {{[-0-9]+}}(%r{{[sb]}}p) ## 8-byte Spill
; CHECK-NEXT: movl {{[0-9]+}}(%rsp), %eax
; CHECK-NEXT: movq %rax, {{[-0-9]+}}(%r{{[sb]}}p) ## 8-byte Spill
; CHECK-NEXT: movl {{[0-9]+}}(%rsp), %ebp
; CHECK-NEXT: movl {{[0-9]+}}(%rsp), %r12d
; CHECK-NEXT: movl {{[0-9]+}}(%rsp), %r15d
; CHECK-NEXT: movl {{[0-9]+}}(%rsp), %r14d
; CHECK-NEXT: movl {{[0-9]+}}(%rsp), %ebx
; CHECK-NEXT: movl {{[0-9]+}}(%rsp), %r11d
; CHECK-NEXT: movl {{[0-9]+}}(%rsp), %r10d
; CHECK-NEXT: movl {{[0-9]+}}(%rsp), %r9d
; CHECK-NEXT: movl {{[0-9]+}}(%rsp), %r8d
; CHECK-NEXT: movl {{[0-9]+}}(%rsp), %edi
; CHECK-NEXT: movl {{[0-9]+}}(%rsp), %esi
; CHECK-NEXT: movl {{[0-9]+}}(%rsp), %edx
; CHECK-NEXT: movl {{[0-9]+}}(%rsp), %ecx
; CHECK-NEXT: movl {{[0-9]+}}(%rsp), %eax

; Re-materialization happened.

; CHECK-NEXT: movabsq $_bar, %r13
; CHECK-NEXT: callq *%r13 ## 96-byte Folded Reload
; CHECK-NEXT: Ltmp0:
; CHECK-NEXT: addq $104, %rsp
; CHECK-NEXT: popq %rbx
; CHECK-NEXT: popq %r12
; CHECK-NEXT: popq %r13
; CHECK-NEXT: popq %r14
; CHECK-NEXT: popq %r15
; CHECK-NEXT: popq %rbp
; CHECK-NEXT: retq

; This is a call to hoist the loading of the target of the call for statepoint.
call void @bar()
br label %entry

entry:
%a64 = zext i32 %a to i64
%b64 = zext i32 %b to i64
%c64 = zext i32 %c to i64
%d64 = zext i32 %d to i64
%e64 = zext i32 %e to i64
%f64 = zext i32 %f to i64
%g64 = zext i32 %g to i64
%h64 = zext i32 %h to i64
%i64 = zext i32 %i to i64
%j64 = zext i32 %j to i64
%k64 = zext i32 %k to i64
%l64 = zext i32 %l to i64
%m64 = zext i32 %m to i64
%n64 = zext i32 %n to i64
%o64 = zext i32 %o to i64
%p64 = zext i32 %p to i64
%q64 = zext i32 %q to i64
%r64 = zext i32 %r to i64
%s64 = zext i32 %s to i64
%t64 = zext i32 %t to i64
%u64 = zext i32 %u to i64
%v64 = zext i32 %v to i64
%w64 = zext i32 %w to i64
%x64 = zext i32 %x to i64
%y64 = zext i32 %y to i64
%z64 = zext i32 %z to i64
%statepoint_token1 = call token (i64, i32, void ()*, i32, i32, ...) @llvm.experimental.gc.statepoint.p0f_isVoidf(i64 2882400000, i32 0, void ()* @bar, i32 0, i32 2, i32 0, i32 26, i64 %a64, i64 %b64, i64 %c64, i64 %d64, i64 %e64, i64 %f64, i64 %g64, i64 %h64, i64 %i64, i64 %j64, i64 %k64, i64 %l64, i64 %m64, i64 %n64, i64 %o64, i64 %p64, i64 %q64, i64 %r64, i64 %s64, i64 %t64, i64 %u64, i64 %v64, i64 %w64, i64 %x64, i64 %y64, i64 %z64)
ret void
}

declare token @llvm.experimental.gc.statepoint.p0f_isVoidf(i64, i32, void ()*, i32, i32, ...)

attributes #0 = { "deopt-lowering"="live-in" }

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