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[2/2][RemoveRedundantDebugValues] Add a Pass that removes redundant DBG_VALUEs
This patch adds the forward scan for finding redundant DBG_VALUEs. This analysis aims to remove redundant DBG_VALUEs by going forward in the basic block by considering the first DBG_VALUE as a valid until its first (location) operand is not clobbered/modified. For example: (1) DBG_VALUE $edi, !"var1", ... (2) <block of code that does affect $edi> (3) DBG_VALUE $edi, !"var1", ... ... in this case, we can remove (3). Differential Revision: https://reviews.llvm.org/D105280
This commit is contained in:
Djordje Todorovic
Djordje Todorovic
parent
57b2fbab2e
commit
140c795b75
@ -6,12 +6,15 @@
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/ADT/DenseMap.h"
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#include "llvm/ADT/DenseSet.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/CodeGen/MachineBasicBlock.h"
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#include "llvm/CodeGen/MachineFunctionPass.h"
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#include "llvm/CodeGen/Passes.h"
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#include "llvm/CodeGen/TargetRegisterInfo.h"
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#include "llvm/CodeGen/TargetSubtargetInfo.h"
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#include "llvm/IR/DebugInfoMetadata.h"
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#include "llvm/IR/Function.h"
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#include "llvm/InitializePasses.h"
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@ -27,6 +30,7 @@
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using namespace llvm;
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STATISTIC(NumRemovedBackward, "Number of DBG_VALUEs removed (backward scan)");
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STATISTIC(NumRemovedForward, "Number of DBG_VALUEs removed (forward scan)");
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namespace {
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@ -66,6 +70,81 @@ RemoveRedundantDebugValues::RemoveRedundantDebugValues()
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initializeRemoveRedundantDebugValuesPass(*PassRegistry::getPassRegistry());
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}
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// This analysis aims to remove redundant DBG_VALUEs by going forward
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// in the basic block by considering the first DBG_VALUE as a valid
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// until its first (location) operand is not clobbered/modified.
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// For example:
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// (1) DBG_VALUE $edi, !"var1", ...
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// (2) <block of code that does affect $edi>
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// (3) DBG_VALUE $edi, !"var1", ...
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// ...
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// in this case, we can remove (3).
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// TODO: Support DBG_VALUE_LIST and other debug instructions.
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static bool reduceDbgValsForwardScan(MachineBasicBlock &MBB) {
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LLVM_DEBUG(dbgs() << "\n == Forward Scan == \n");
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SmallVector<MachineInstr *, 8> DbgValsToBeRemoved;
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DenseMap<DebugVariable, std::pair<MachineOperand *, const DIExpression *>>
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VariableMap;
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const auto *TRI = MBB.getParent()->getSubtarget().getRegisterInfo();
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for (auto &MI : MBB) {
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if (MI.isDebugValue()) {
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DebugVariable Var(MI.getDebugVariable(), NoneType(),
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MI.getDebugLoc()->getInlinedAt());
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auto VMI = VariableMap.find(Var);
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// Just stop tracking this variable, until we cover DBG_VALUE_LIST.
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// 1 DBG_VALUE $rax, "x", DIExpression()
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// ...
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// 2 DBG_VALUE_LIST "x", DIExpression(...), $rax, $rbx
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// ...
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// 3 DBG_VALUE $rax, "x", DIExpression()
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if (MI.isDebugValueList() && VMI != VariableMap.end()) {
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VariableMap.erase(VMI);
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continue;
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}
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MachineOperand &Loc = MI.getDebugOperand(0);
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if (!Loc.isReg()) {
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// If it it's not a register, just stop tracking such variable.
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if (VMI != VariableMap.end())
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VariableMap.erase(VMI);
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continue;
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}
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// We have found a new value for a variable.
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if (VMI == VariableMap.end() ||
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VMI->second.first->getReg() != Loc.getReg() ||
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VMI->second.second != MI.getDebugExpression()) {
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VariableMap[Var] = {&Loc, MI.getDebugExpression()};
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continue;
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}
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// Found an identical DBG_VALUE, so it can be considered
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// for later removal.
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DbgValsToBeRemoved.push_back(&MI);
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}
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if (MI.isMetaInstruction())
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continue;
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// Stop tracking any location that is clobbered by this instruction.
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for (auto &Var : VariableMap) {
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auto &LocOp = Var.second.first;
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if (MI.modifiesRegister(LocOp->getReg(), TRI))
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VariableMap.erase(Var.first);
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}
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}
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for (auto &Instr : DbgValsToBeRemoved) {
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LLVM_DEBUG(dbgs() << "removing "; Instr->dump());
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Instr->eraseFromParent();
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++NumRemovedForward;
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}
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return !DbgValsToBeRemoved.empty();
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}
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// This analysis aims to remove redundant DBG_VALUEs by going backward
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// in the basic block and removing all but the last DBG_VALUE for any
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// given variable in a set of consecutive DBG_VALUE instructions.
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@ -129,8 +208,10 @@ bool RemoveRedundantDebugValues::reduceDbgValues(MachineFunction &MF) {
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bool Changed = false;
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for (auto &MBB : MF)
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for (auto &MBB : MF) {
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Changed |= reduceDbgValsBackwardScan(MBB);
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Changed |= reduceDbgValsForwardScan(MBB);
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}
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return Changed;
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}
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@ -29,7 +29,6 @@ define dso_local void @test(float* nocapture readonly %Fptr, <4 x float>* nocapt
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; CHECK-NEXT: xvcvdpsp 34, 0
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; CHECK-NEXT: xvcvdpsp 35, 1
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; CHECK-NEXT: vmrgew 2, 2, 3
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; CHECK-NEXT: #DEBUG_VALUE: test:Vptr <- $x4
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; CHECK-NEXT: .loc 1 3 9 is_stmt 0
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; CHECK-NEXT: stvx 2, 0, 4
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; CHECK-NEXT: .loc 1 4 1 is_stmt 1
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@ -1,13 +1,17 @@
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# RUN: llc %s -o - -run-pass=removeredundantdebugvalues | FileCheck %s
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# RUN: llc %s -o - -run-pass=removeredundantdebugvalues | FileCheck --implicit-check-not=DBG_VALUE %s
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## This checks that the RemoveRedundantDebugValues removes redundant
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## DBG_VALUEs.
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## DBG_VALUEs. The MIR was hand-written, and foo{[2-6]}() are just
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## copies of foo(), with an extra instruction that modifies the $edi register
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## and extra (artificial) DBG_VALUE and DBG_VALUE_LIST instructions.
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# CHECK-LABEL: foo
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# CHECK-LABEL: bb.0.entry:
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# CHECK: DBG_VALUE $edi
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# CHECK-NOT: DBG_VALUE $edi
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# CHECK: frame-setup PUSH64r
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# CHECK: MOV32mr $rip, 1, $noreg
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# CHECK-NOT: DBG_VALUE $edi
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# CHECK-LABEL: foo6
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# CHECK-LABEL: bb.0.entry:
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@ -15,6 +19,30 @@
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# CHECK: DBG_VALUE 1
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# CHECK: frame-setup PUSH64r
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# CHECK-LABEL: foo2
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# CHECK-LABEL: bb.0.entry:
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# CHECK: DBG_VALUE $edi
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# CHECK: MOV32mr $rip, 1, $noreg
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# CHECK: DBG_VALUE $edi
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# CHECK-LABEL: foo3
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# CHECK-LABEL: bb.0.entry:
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# CHECK: DBG_VALUE $edi, {{.*}}, !DIExpression(DW_OP_LLVM_fragment, 0, 32)
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# CHECK: DBG_VALUE $esi, {{.*}}, !DIExpression()
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# CHECK: DBG_VALUE $edi, {{.*}}, !DIExpression(DW_OP_LLVM_fragment, 0, 32)
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# CHECK-LABEL: foo4
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# CHECK-LABEL: bb.0.entry:
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# CHECK: DBG_VALUE $edi, {{.*}}, !DIExpression(DW_OP_LLVM_fragment, 0, 32)
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# CHECK: DBG_VALUE_LIST !{{.*}}
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# CHECK: DBG_VALUE $edi, {{.*}}, !DIExpression(DW_OP_LLVM_fragment, 0, 32)
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# CHECK-LABEL: foo5
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# CHECK-LABEL: bb.0.entry:
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# CHECK: DBG_VALUE $edi, {{.*}}, !DIExpression(DW_OP_LLVM_fragment, 0, 32)
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# CHECK: DBG_VALUE 0, {{.*}}, !DIExpression()
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# CHECK: DBG_VALUE $edi, {{.*}}, !DIExpression(DW_OP_LLVM_fragment, 0, 32)
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--- |
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; ModuleID = 'test.ll'
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source_filename = "test.c"
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@ -43,6 +71,42 @@
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ret i32 0, !dbg !35
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}
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; Function Attrs: nounwind uwtable
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define dso_local i32 @foo2(i32 %param) local_unnamed_addr !dbg !26 {
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entry:
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store i32 %param, i32* @side_effect, align 4, !dbg !27
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%0 = load i32, i32* @value, align 4, !dbg !27
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tail call void @bar(i32 %0), !dbg !27
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ret i32 0, !dbg !27
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}
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; Function Attrs: nounwind uwtable
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define dso_local i32 @foo3(i32 %param) local_unnamed_addr !dbg !28 {
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entry:
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store i32 %param, i32* @side_effect, align 4, !dbg !29
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%0 = load i32, i32* @value, align 4, !dbg !29
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tail call void @bar(i32 %0), !dbg !29
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ret i32 0, !dbg !29
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}
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; Function Attrs: nounwind uwtable
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define dso_local i32 @foo4(i32 %param) local_unnamed_addr !dbg !30 {
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entry:
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store i32 %param, i32* @side_effect, align 4, !dbg !31
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%0 = load i32, i32* @value, align 4, !dbg !31
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tail call void @bar(i32 %0), !dbg !31
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ret i32 0, !dbg !31
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}
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; Function Attrs: nounwind uwtable
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define dso_local i32 @foo5(i32 %param) local_unnamed_addr !dbg !32 {
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entry:
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store i32 %param, i32* @side_effect, align 4, !dbg !33
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%0 = load i32, i32* @value, align 4, !dbg !33
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tail call void @bar(i32 %0), !dbg !33
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ret i32 0, !dbg !33
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}
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declare !dbg !23 dso_local void @bar(i32) local_unnamed_addr
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; Function Attrs: nofree nosync nounwind readnone speculatable willreturn
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@ -74,6 +138,14 @@
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!23 = !DISubprogram(name: "bar", scope: !1, file: !1, line: 1, type: !24, flags: DIFlagPrototyped, spFlags: DISPFlagOptimized, retainedNodes: !2)
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!24 = !DISubroutineType(types: !25)
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!25 = !{null, !11}
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!26 = distinct !DISubprogram(name: "foo2", scope: !1, file: !1, line: 4, type: !9, scopeLine: 4, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !12)
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!27 = !DILocation(line: 0, scope: !26)
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!28 = distinct !DISubprogram(name: "foo3", scope: !1, file: !1, line: 4, type: !9, scopeLine: 4, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !12)
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!29 = !DILocation(line: 0, scope: !28)
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!30 = distinct !DISubprogram(name: "foo4", scope: !1, file: !1, line: 4, type: !9, scopeLine: 4, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !12)
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!31 = !DILocation(line: 0, scope: !30)
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!32 = distinct !DISubprogram(name: "foo5", scope: !1, file: !1, line: 4, type: !9, scopeLine: 4, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !12)
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!33 = !DILocation(line: 0, scope: !32)
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!34 = distinct !DISubprogram(name: "foo6", scope: !1, file: !1, line: 4, type: !9, scopeLine: 4, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !12)
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!35 = !DILocation(line: 0, scope: !34)
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@ -99,6 +171,95 @@ body: |
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CFI_INSTRUCTION def_cfa_offset 8, debug-location !22
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RETQ killed $eax, debug-location !22
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...
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---
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name: foo2
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alignment: 16
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liveins:
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- { reg: '$edi', virtual-reg: '' }
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body: |
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bb.0.entry:
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liveins: $edi, $esi
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DBG_VALUE $edi, $noreg, !13, !DIExpression(), debug-location !14
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DBG_VALUE $edi, $noreg, !13, !DIExpression(), debug-location !14
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frame-setup PUSH64r undef $rax, implicit-def $rsp, implicit $rsp
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CFI_INSTRUCTION def_cfa_offset 16
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MOV32mr $rip, 1, $noreg, @side_effect, $noreg, killed renamable $esi, debug-location !15 :: (store 4 into @side_effect)
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renamable $edi = MOV32rm $rip, 1, $noreg, @value, $noreg, debug-location !20 :: (dereferenceable load 4 from @value)
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DBG_VALUE $edi, $noreg, !13, !DIExpression(), debug-location !14
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CALL64pcrel32 @bar, csr_64, implicit $rsp, implicit $ssp, implicit $edi, implicit-def $rsp, implicit-def $ssp, debug-location !21
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$eax = XOR32rr undef $eax, undef $eax, implicit-def dead $eflags, debug-location !22
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$rcx = frame-destroy POP64r implicit-def $rsp, implicit $rsp, debug-location !22
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CFI_INSTRUCTION def_cfa_offset 8, debug-location !22
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RETQ killed $eax, debug-location !22
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...
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---
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name: foo3
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alignment: 16
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liveins:
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- { reg: '$edi', virtual-reg: '' }
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body: |
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bb.0.entry:
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liveins: $edi, $esi
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DBG_VALUE $edi, $noreg, !13, !DIExpression(DW_OP_LLVM_fragment, 0, 32), debug-location !14
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frame-setup PUSH64r undef $rax, implicit-def $rsp, implicit $rsp
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CFI_INSTRUCTION def_cfa_offset 16
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MOV32mr $rip, 1, $noreg, @side_effect, $noreg, killed renamable $esi, debug-location !15 :: (store 4 into @side_effect)
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renamable $esi = MOV32rm $rip, 1, $noreg, @value, $noreg, debug-location !20 :: (dereferenceable load 4 from @value)
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DBG_VALUE $esi, $noreg, !13, !DIExpression(), debug-location !14
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$eax = XOR32rr undef $eax, undef $eax, implicit-def dead $eflags, debug-location !22
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DBG_VALUE $edi, $noreg, !13, !DIExpression(DW_OP_LLVM_fragment, 0, 32), debug-location !14
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$rcx = frame-destroy POP64r implicit-def $rsp, implicit $rsp, debug-location !22
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CFI_INSTRUCTION def_cfa_offset 8, debug-location !22
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RETQ killed $eax, debug-location !22
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...
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---
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name: foo4
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alignment: 16
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liveins:
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- { reg: '$edi', virtual-reg: '' }
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body: |
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bb.0.entry:
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liveins: $edi, $esi
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DBG_VALUE $edi, $noreg, !13, !DIExpression(DW_OP_LLVM_fragment, 0, 32), debug-location !14
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frame-setup PUSH64r undef $rax, implicit-def $rsp, implicit $rsp
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CFI_INSTRUCTION def_cfa_offset 16
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MOV32mr $rip, 1, $noreg, @side_effect, $noreg, killed renamable $esi, debug-location !15 :: (store 4 into @side_effect)
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renamable $esi = MOV32rm $rip, 1, $noreg, @value, $noreg, debug-location !20 :: (dereferenceable load 4 from @value)
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DBG_VALUE_LIST !13, !DIExpression(DW_OP_LLVM_arg, 0, DW_OP_LLVM_arg, 1, DW_OP_plus, DW_OP_stack_value), $edi, $esi, debug-location !14
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$eax = XOR32rr undef $eax, undef $eax, implicit-def dead $eflags, debug-location !22
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DBG_VALUE $edi, $noreg, !13, !DIExpression(DW_OP_LLVM_fragment, 0, 32), debug-location !14
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$rcx = frame-destroy POP64r implicit-def $rsp, implicit $rsp, debug-location !22
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CFI_INSTRUCTION def_cfa_offset 8, debug-location !22
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RETQ killed $eax, debug-location !22
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...
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---
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name: foo5
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alignment: 16
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liveins:
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- { reg: '$edi', virtual-reg: '' }
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body: |
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bb.0.entry:
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liveins: $edi, $esi
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DBG_VALUE $edi, $noreg, !13, !DIExpression(DW_OP_LLVM_fragment, 0, 32), debug-location !14
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frame-setup PUSH64r undef $rax, implicit-def $rsp, implicit $rsp
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CFI_INSTRUCTION def_cfa_offset 16
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MOV32mr $rip, 1, $noreg, @side_effect, $noreg, killed renamable $esi, debug-location !15 :: (store 4 into @side_effect)
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renamable $esi = MOV32rm $rip, 1, $noreg, @value, $noreg, debug-location !20 :: (dereferenceable load 4 from @value)
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DBG_VALUE 0, $noreg, !13, !DIExpression(), debug-location !14
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$eax = XOR32rr undef $eax, undef $eax, implicit-def dead $eflags, debug-location !22
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DBG_VALUE $edi, $noreg, !13, !DIExpression(DW_OP_LLVM_fragment, 0, 32), debug-location !14
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$rcx = frame-destroy POP64r implicit-def $rsp, implicit $rsp, debug-location !22
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CFI_INSTRUCTION def_cfa_offset 8, debug-location !22
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RETQ killed $eax, debug-location !22
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...
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---
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name: foo6
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