[llvm] r203829 - Fix for http://llvm.org/bugs/show_bug.cgi?id=18590
Ekaterina Romanova
katya_romanova at playstation.sony.com
Thu Mar 13 11:47:13 PDT 2014
Author: kromanova
Date: Thu Mar 13 13:47:12 2014
New Revision: 203829
URL: http://llvm.org/viewvc/llvm-project?rev=203829&view=rev
Log:
Fix for http://llvm.org/bugs/show_bug.cgi?id=18590
This patch fixes the bug in peephole optimization that folds a load which defines one vreg into the one and only use of that vreg. With debug info, a DBG_VALUE that referenced the vreg considered to be a use, preventing the optimization. The fix is to ignore DBG_VALUE's during the optimization, and undef a DBG_VALUE that references a vreg that gets removed.
Patch by Trevor Smigiel!
Added:
llvm/trunk/test/CodeGen/X86/dbg-changes-codegen.ll
Modified:
llvm/trunk/include/llvm/CodeGen/MachineRegisterInfo.h
llvm/trunk/lib/CodeGen/DeadMachineInstructionElim.cpp
llvm/trunk/lib/CodeGen/MachineRegisterInfo.cpp
llvm/trunk/lib/CodeGen/PeepholeOptimizer.cpp
Modified: llvm/trunk/include/llvm/CodeGen/MachineRegisterInfo.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/CodeGen/MachineRegisterInfo.h?rev=203829&r1=203828&r2=203829&view=diff
==============================================================================
--- llvm/trunk/include/llvm/CodeGen/MachineRegisterInfo.h (original)
+++ llvm/trunk/include/llvm/CodeGen/MachineRegisterInfo.h Thu Mar 13 13:47:12 2014
@@ -510,6 +510,10 @@ public:
return Hint.first ? 0 : Hint.second;
}
+ /// markUsesInDebugValueAsUndef - Mark every DBG_VALUE referencing the
+ /// specified register as undefined which causes the DBG_VALUE to be
+ /// deleted during LiveDebugVariables analysis.
+ void markUsesInDebugValueAsUndef(unsigned Reg) const;
//===--------------------------------------------------------------------===//
// Physical Register Use Info
Modified: llvm/trunk/lib/CodeGen/DeadMachineInstructionElim.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/DeadMachineInstructionElim.cpp?rev=203829&r1=203828&r2=203829&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/DeadMachineInstructionElim.cpp (original)
+++ llvm/trunk/lib/CodeGen/DeadMachineInstructionElim.cpp Thu Mar 13 13:47:12 2014
@@ -127,17 +127,7 @@ bool DeadMachineInstructionElim::runOnMa
unsigned Reg = MO.getReg();
if (!TargetRegisterInfo::isVirtualRegister(Reg))
continue;
- MachineRegisterInfo::use_iterator nextI;
- for (MachineRegisterInfo::use_iterator I = MRI->use_begin(Reg),
- E = MRI->use_end(); I!=E; I=nextI) {
- nextI = std::next(I); // I is invalidated by the setReg
- MachineOperand& Use = I.getOperand();
- MachineInstr *UseMI = Use.getParent();
- if (UseMI==MI)
- continue;
- assert(Use.isDebug());
- UseMI->getOperand(0).setReg(0U);
- }
+ MRI->markUsesInDebugValueAsUndef(Reg);
}
AnyChanges = true;
MI->eraseFromParent();
Modified: llvm/trunk/lib/CodeGen/MachineRegisterInfo.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/MachineRegisterInfo.cpp?rev=203829&r1=203828&r2=203829&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/MachineRegisterInfo.cpp (original)
+++ llvm/trunk/lib/CodeGen/MachineRegisterInfo.cpp Thu Mar 13 13:47:12 2014
@@ -414,3 +414,18 @@ bool MachineRegisterInfo::isConstantPhys
return false;
return true;
}
+
+/// markUsesInDebugValueAsUndef - Mark every DBG_VALUE referencing the
+/// specified register as undefined which causes the DBG_VALUE to be
+/// deleted during LiveDebugVariables analysis.
+void MachineRegisterInfo::markUsesInDebugValueAsUndef(unsigned Reg) const {
+ // Mark any DBG_VALUE that uses Reg as undef (but don't delete it.)
+ MachineRegisterInfo::use_iterator nextI;
+ for (use_iterator I = use_begin(Reg), E = use_end(); I != E; I = nextI) {
+ nextI = std::next(I); // I is invalidated by the setReg
+ MachineOperand& Use = I.getOperand();
+ MachineInstr *UseMI = Use.getParent();
+ if (UseMI->isDebugValue())
+ UseMI->getOperand(0).setReg(0U);
+ }
+}
Modified: llvm/trunk/lib/CodeGen/PeepholeOptimizer.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/PeepholeOptimizer.cpp?rev=203829&r1=203828&r2=203829&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/PeepholeOptimizer.cpp (original)
+++ llvm/trunk/lib/CodeGen/PeepholeOptimizer.cpp Thu Mar 13 13:47:12 2014
@@ -505,12 +505,12 @@ bool PeepholeOptimizer::isLoadFoldable(M
return false;
unsigned Reg = MI->getOperand(0).getReg();
- // To reduce compilation time, we check MRI->hasOneUse when inserting
+ // To reduce compilation time, we check MRI->hasOneNonDBGUse when inserting
// loads. It should be checked when processing uses of the load, since
// uses can be removed during peephole.
if (!MI->getOperand(0).getSubReg() &&
TargetRegisterInfo::isVirtualRegister(Reg) &&
- MRI->hasOneUse(Reg)) {
+ MRI->hasOneNonDBGUse(Reg)) {
FoldAsLoadDefReg = Reg;
return true;
}
@@ -594,10 +594,14 @@ bool PeepholeOptimizer::runOnMachineFunc
++MII;
LocalMIs.insert(MI);
+ // Skip debug values. They should not affect this peephole optimization.
+ if (MI->isDebugValue())
+ continue;
+
// If there exists an instruction which belongs to the following
// categories, we will discard the load candidate.
if (MI->isPosition() || MI->isPHI() || MI->isImplicitDef() ||
- MI->isKill() || MI->isInlineAsm() || MI->isDebugValue() ||
+ MI->isKill() || MI->isInlineAsm() ||
MI->hasUnmodeledSideEffects()) {
FoldAsLoadDefReg = 0;
continue;
@@ -633,6 +637,9 @@ bool PeepholeOptimizer::runOnMachineFunc
if (!isLoadFoldable(MI, FoldAsLoadDefReg) && FoldAsLoadDefReg) {
// We need to fold load after optimizeCmpInstr, since optimizeCmpInstr
// can enable folding by converting SUB to CMP.
+ // Save FoldAsLoadDefReg because optimizeLoadInstr() resets it and we
+ // need it for markUsesInDebugValueAsUndef().
+ unsigned FoldedReg = FoldAsLoadDefReg;
MachineInstr *DefMI = 0;
MachineInstr *FoldMI = TII->optimizeLoadInstr(MI, MRI,
FoldAsLoadDefReg, DefMI);
@@ -645,6 +652,7 @@ bool PeepholeOptimizer::runOnMachineFunc
LocalMIs.insert(FoldMI);
MI->eraseFromParent();
DefMI->eraseFromParent();
+ MRI->markUsesInDebugValueAsUndef(FoldedReg);
++NumLoadFold;
// MI is replaced with FoldMI.
Added: llvm/trunk/test/CodeGen/X86/dbg-changes-codegen.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/dbg-changes-codegen.ll?rev=203829&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/X86/dbg-changes-codegen.ll (added)
+++ llvm/trunk/test/CodeGen/X86/dbg-changes-codegen.ll Thu Mar 13 13:47:12 2014
@@ -0,0 +1,83 @@
+; RUN: llc < %s -march=x86-64 | FileCheck %s
+
+; The Peephole optimizer should fold the load into the cmp even with debug info.
+; CHECK-LABEL: _ZN3Foo3batEv
+; CHECK-NOT: movq pfoo
+; CHECK: cmpq {{%[a-z]+}}, pfoo(%rip)
+;
+; CHECK-LABEL: _Z3bazv
+; CHECK-NOT: movq wibble2
+; CHECK: cmpq {{%[a-z]+}}, wibble2(%rip)
+
+; Regenerate test with this command:
+; clang -emit-llvm -S -O2 -g
+; from this source:
+; struct Foo {
+; bool bat();
+; bool operator==(Foo &arg) { return (this == &arg); }
+; };
+; Foo *pfoo;
+; bool Foo::bat() { return (*this == *pfoo); }
+;
+; struct Wibble {
+; int x;
+; } *wibble1, *wibble2;
+; struct Flibble {
+; void bar(Wibble *c) {
+; if (c < wibble2)
+; wibble2 = 0;
+; c->x = 0;
+; }
+; } flibble;
+; void baz() { flibble.bar(wibble1); }
+
+%struct.Foo = type { i8 }
+%struct.Wibble = type { i32 }
+%struct.Flibble = type { i8 }
+
+ at pfoo = global %struct.Foo* null, align 8
+ at wibble1 = global %struct.Wibble* null, align 8
+ at wibble2 = global %struct.Wibble* null, align 8
+ at flibble = global %struct.Flibble zeroinitializer, align 1
+
+; Function Attrs: nounwind readonly uwtable
+define zeroext i1 @_ZN3Foo3batEv(%struct.Foo* %this) #0 align 2 {
+entry:
+ %0 = load %struct.Foo** @pfoo, align 8
+ tail call void @llvm.dbg.value(metadata !{%struct.Foo* %0}, i64 0, metadata !62)
+ %cmp.i = icmp eq %struct.Foo* %0, %this
+ ret i1 %cmp.i
+}
+
+; Function Attrs: nounwind uwtable
+define void @_Z3bazv() #1 {
+entry:
+ %0 = load %struct.Wibble** @wibble1, align 8
+ tail call void @llvm.dbg.value(metadata !64, i64 0, metadata !65)
+ %1 = load %struct.Wibble** @wibble2, align 8
+ %cmp.i = icmp ugt %struct.Wibble* %1, %0
+ br i1 %cmp.i, label %if.then.i, label %_ZN7Flibble3barEP6Wibble.exit
+
+if.then.i: ; preds = %entry
+ store %struct.Wibble* null, %struct.Wibble** @wibble2, align 8
+ br label %_ZN7Flibble3barEP6Wibble.exit
+
+_ZN7Flibble3barEP6Wibble.exit: ; preds = %entry, %if.then.i
+ %x.i = getelementptr inbounds %struct.Wibble* %0, i64 0, i32 0
+ store i32 0, i32* %x.i, align 4
+ ret void
+}
+
+; Function Attrs: nounwind readnone
+declare void @llvm.dbg.value(metadata, i64, metadata) #2
+
+attributes #0 = { nounwind readonly uwtable "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-frame-pointer-elim-non-leaf"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #1 = { nounwind uwtable "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-frame-pointer-elim-non-leaf"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #2 = { nounwind readnone }
+
+
+!17 = metadata !{i32 786448, null, null, null, i32 0, i64 0, i64 0, i64 0, i32 0, null} ; [ DW_TAG_reference_type ] [line 0, size 0, align 0, offset 0] [from Foo]
+!45 = metadata !{i32 786447, null, null, metadata !"", i32 0, i64 64, i64 64, i64 0, i32 0, null} ; [ DW_TAG_pointer_type ] [line 0, size 64, align 64, offset 0] [from Flibble]
+!62 = metadata !{i32 786689, null, metadata !"arg", null, i32 33554436, metadata !17, i32 0, null} ; [ DW_TAG_arg_variable ] [arg] [line 4]
+!64 = metadata !{%struct.Flibble* undef}
+!65 = metadata !{i32 786689, null, metadata !"this", null, i32 16777229, metadata !45, i32 1088, null} ; [ DW_TAG_arg_variable ] [this] [line 13]
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