[llvm] r247042 - Fix for bz24500: Avoid non-deterministic code generation triggered by the x86 call frame optimization
Andrew Kaylor via llvm-commits
llvm-commits at lists.llvm.org
Tue Sep 8 11:18:46 PDT 2015
Author: akaylor
Date: Tue Sep 8 13:18:46 2015
New Revision: 247042
URL: http://llvm.org/viewvc/llvm-project?rev=247042&view=rev
Log:
Fix for bz24500: Avoid non-deterministic code generation triggered by the x86 call frame optimization
Patch by Dave Kreitzer
Differential Revision: http://reviews.llvm.org/D12620
Modified:
llvm/trunk/lib/Target/X86/X86CallFrameOptimization.cpp
Modified: llvm/trunk/lib/Target/X86/X86CallFrameOptimization.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86CallFrameOptimization.cpp?rev=247042&r1=247041&r2=247042&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86CallFrameOptimization.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86CallFrameOptimization.cpp Tue Sep 8 13:18:46 2015
@@ -53,10 +53,13 @@ private:
// Information we know about a particular call site
struct CallContext {
CallContext()
- : Call(nullptr), SPCopy(nullptr), ExpectedDist(0),
+ : FrameSetup(nullptr), Call(nullptr), SPCopy(nullptr), ExpectedDist(0),
MovVector(4, nullptr), NoStackParams(false), UsePush(false){}
- // Actuall call instruction
+ // Iterator referring to the frame setup instruction
+ MachineBasicBlock::iterator FrameSetup;
+
+ // Actual call instruction
MachineInstr *Call;
// A copy of the stack pointer
@@ -75,17 +78,16 @@ private:
bool UsePush;
};
- typedef DenseMap<MachineInstr *, CallContext> ContextMap;
+ typedef SmallVector<CallContext, 8> ContextVector;
bool isLegal(MachineFunction &MF);
- bool isProfitable(MachineFunction &MF, ContextMap &CallSeqMap);
+ bool isProfitable(MachineFunction &MF, ContextVector &CallSeqMap);
void collectCallInfo(MachineFunction &MF, MachineBasicBlock &MBB,
MachineBasicBlock::iterator I, CallContext &Context);
- bool adjustCallSequence(MachineFunction &MF, MachineBasicBlock::iterator I,
- const CallContext &Context);
+ bool adjustCallSequence(MachineFunction &MF, const CallContext &Context);
MachineInstr *canFoldIntoRegPush(MachineBasicBlock::iterator FrameSetup,
unsigned Reg);
@@ -161,7 +163,7 @@ bool X86CallFrameOptimization::isLegal(M
// Check whether this trasnformation is profitable for a particular
// function - in terms of code size.
bool X86CallFrameOptimization::isProfitable(MachineFunction &MF,
- ContextMap &CallSeqMap) {
+ ContextVector &CallSeqVector) {
// This transformation is always a win when we do not expect to have
// a reserved call frame. Under other circumstances, it may be either
// a win or a loss, and requires a heuristic.
@@ -176,14 +178,14 @@ bool X86CallFrameOptimization::isProfita
unsigned StackAlign = TFL->getStackAlignment();
int64_t Advantage = 0;
- for (auto CC : CallSeqMap) {
+ for (auto CC : CallSeqVector) {
// Call sites where no parameters are passed on the stack
// do not affect the cost, since there needs to be no
// stack adjustment.
- if (CC.second.NoStackParams)
+ if (CC.NoStackParams)
continue;
- if (!CC.second.UsePush) {
+ if (!CC.UsePush) {
// If we don't use pushes for a particular call site,
// we pay for not having a reserved call frame with an
// additional sub/add esp pair. The cost is ~3 bytes per instruction,
@@ -196,11 +198,11 @@ bool X86CallFrameOptimization::isProfita
// We'll need a add after the call.
Advantage -= 3;
// If we have to realign the stack, we'll also need and sub before
- if (CC.second.ExpectedDist % StackAlign)
+ if (CC.ExpectedDist % StackAlign)
Advantage -= 3;
// Now, for each push, we save ~3 bytes. For small constants, we actually,
// save more (up to 5 bytes), but 3 should be a good approximation.
- Advantage += (CC.second.ExpectedDist / 4) * 3;
+ Advantage += (CC.ExpectedDist / 4) * 3;
}
}
@@ -219,21 +221,22 @@ bool X86CallFrameOptimization::runOnMach
bool Changed = false;
- ContextMap CallSeqMap;
+ ContextVector CallSeqVector;
for (MachineFunction::iterator BB = MF.begin(), E = MF.end(); BB != E; ++BB)
for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ++I)
if (I->getOpcode() == FrameSetupOpcode) {
- CallContext &Context = CallSeqMap[I];
+ CallContext Context;
collectCallInfo(MF, *BB, I, Context);
+ CallSeqVector.push_back(Context);
}
- if (!isProfitable(MF, CallSeqMap))
+ if (!isProfitable(MF, CallSeqVector))
return false;
- for (auto CC : CallSeqMap)
- if (CC.second.UsePush)
- Changed |= adjustCallSequence(MF, CC.first, CC.second);
+ for (auto CC : CallSeqVector)
+ if (CC.UsePush)
+ Changed |= adjustCallSequence(MF, CC);
return Changed;
}
@@ -309,6 +312,7 @@ void X86CallFrameOptimization::collectCa
// We expect to enter this at the beginning of a call sequence
assert(I->getOpcode() == TII->getCallFrameSetupOpcode());
MachineBasicBlock::iterator FrameSetup = I++;
+ Context.FrameSetup = FrameSetup;
// How much do we adjust the stack? This puts an upper bound on
// the number of parameters actually passed on it.
@@ -430,16 +434,15 @@ void X86CallFrameOptimization::collectCa
}
bool X86CallFrameOptimization::adjustCallSequence(MachineFunction &MF,
- MachineBasicBlock::iterator I,
const CallContext &Context) {
// Ok, we can in fact do the transformation for this call.
// Do not remove the FrameSetup instruction, but adjust the parameters.
// PEI will end up finalizing the handling of this.
- MachineBasicBlock::iterator FrameSetup = I;
- MachineBasicBlock &MBB = *(I->getParent());
+ MachineBasicBlock::iterator FrameSetup = Context.FrameSetup;
+ MachineBasicBlock &MBB = *(FrameSetup->getParent());
FrameSetup->getOperand(1).setImm(Context.ExpectedDist);
- DebugLoc DL = I->getDebugLoc();
+ DebugLoc DL = FrameSetup->getDebugLoc();
// Now, iterate through the vector in reverse order, and replace the movs
// with pushes. MOVmi/MOVmr doesn't have any defs, so no need to
// replace uses.
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