From fc64d978d758579028918348d14253bab8b97000 Mon Sep 17 00:00:00 2001
From: Clark Coleman <clc@zephyr-software.com>
Date: Mon, 5 Oct 2020 17:08:01 -0400
Subject: [PATCH] SPARK: Add INVERTED_LOOP_BACK type, detect it, follow its
successor when StaysInLoop is true.
---
include/base/SMPBasicBlock.h | 1 +
include/base/SMPDataFlowAnalysis.h | 3 ++-
src/base/SMPBasicBlock.cpp | 23 ++++++++++++++++++++++-
src/base/SMPDataFlowAnalysis.cpp | 4 ++--
src/base/SMPFunction.cpp | 19 ++++++++++++++++---
src/base/SMPInstr.cpp | 2 +-
6 files changed, 44 insertions(+), 8 deletions(-)
diff --git a/include/base/SMPBasicBlock.h b/include/base/SMPBasicBlock.h
index 5080d4a7..067a4782 100644
--- a/include/base/SMPBasicBlock.h
+++ b/include/base/SMPBasicBlock.h
@@ -351,6 +351,7 @@ public:
bool IsBlockPred(int BlockNum) const; // Is BlockNum a predecessor block of this block
bool HasLoopHeadAsSuccessor(int &HeadBlockNum) const; // block has HeadBlockNum as successor, which is a loop header
bool HasLoopHeadWithInvertedExitAsSuccessor(void) const; // block has loop head successor that ends with INVERTED_LOOP_EXIT
+ bool HasInvertedLoopBack(void) const; // COND_BRANCH falls through to loop header of innermost loop containing this block
bool IsLiveIn(const STARSOpndTypePtr &CurrOp);
inline bool IsLiveOut(const STARSOpndTypePtr &CurrOp) const {
return (LiveOutSet.end() != LiveOutSet.find(CurrOp));
diff --git a/include/base/SMPDataFlowAnalysis.h b/include/base/SMPDataFlowAnalysis.h
index fef5ea87..381c58ef 100644
--- a/include/base/SMPDataFlowAnalysis.h
+++ b/include/base/SMPDataFlowAnalysis.h
@@ -671,7 +671,8 @@ enum ControlFlowType {
JUMP_TO_SWITCH_INDIR_JUMP = 9, // jump around default case or preliminary calculations to INDIR_JUMP block for switch
SHORT_CIRCUIT_BRANCH = 10, // any branch in short-circuit conditional evaluation
SHORT_CIRCUIT_LOOP_EXIT = 11, // short-circuit compound conditional expression that exits loop when true
- INVERTED_LOOP_EXIT = 12 // COND_BRANCH falls out of loop via headerblock, branch taken stays in loop; code layout puts headerblock at bottom
+ INVERTED_LOOP_EXIT = 12, // COND_BRANCH falls out of loop via headerblock, branch taken stays in loop; code layout puts headerblock at bottom
+ INVERTED_LOOP_BACK = 13 // COND_BRANCH falls through to loop headerblock of its containing innermost loop
};
// Strings for debug dumps of ControlFlowType.
diff --git a/src/base/SMPBasicBlock.cpp b/src/base/SMPBasicBlock.cpp
index d7471f75..f5329462 100644
--- a/src/base/SMPBasicBlock.cpp
+++ b/src/base/SMPBasicBlock.cpp
@@ -1139,6 +1139,26 @@ bool SMPBasicBlock::HasLoopHeadWithInvertedExitAsSuccessor(void) const {
return OddFlowCase;
} // end of SMPBasicBlock::HasLoopHeadWithInvertedExitAsSuccessor()
+// COND_BRANCH falls through to loop header of innermost loop containing this block
+bool SMPBasicBlock::HasInvertedLoopBack(void) const {
+ bool FallsThroughToLoopHead = false;
+ if (this->HasConditionalBranch()) {
+ list<SMPBasicBlock *>::const_iterator SuccIter = this->GetCondNonFallThroughSucc();
+ SMPBasicBlock *SuccBlock = (*SuccIter);
+ assert(nullptr != SuccBlock);
+ int TargetBlockNum = SuccBlock->GetNumber();
+ SuccIter = this->GetCondOtherSucc(TargetBlockNum);
+ SuccBlock = (*SuccIter);
+ assert(nullptr != SuccBlock);
+ int FallThroughBlockNum = SuccBlock->GetNumber();
+ if (SuccBlock->IsLoopHeaderBlock()) {
+ FallsThroughToLoopHead = (SuccBlock->IsLoopHeaderBlock() && this->GetFunc()->AreBlocksInSameLoops(FallThroughBlockNum, this->GetNumber()));
+ }
+ }
+
+ return FallsThroughToLoopHead;
+} // end of SMPBasicBlock::HasInvertedLoopBack()
+
// Determine if CurrOp is LiveIn; if LiveIn set is stale, recompute.
bool SMPBasicBlock::IsLiveIn(const STARSOpndTypePtr &CurrOp) {
@@ -2683,7 +2703,8 @@ bool SMPBasicBlock::DoesDefControlLoopFlow(const STARSOpndTypePtr &DefOp, int De
if (FlowType == COND_BRANCH) {
STARS_ea_t LastAddr = LastInst->GetAddr();
ControlFlowType LastBranchType = this->GetFunc()->GetControlFlowType(LastAddr);
- if ((LastBranchType != LOOP_EXIT) && (LastBranchType != LOOP_BACK)) {
+ bool IsLoopBack = ((LastBranchType == LOOP_BACK) || (LastBranchType == INVERTED_LOOP_BACK));
+ if ((LastBranchType != LOOP_EXIT) && (!IsLoopBack)) {
return false;
}
}
diff --git a/src/base/SMPDataFlowAnalysis.cpp b/src/base/SMPDataFlowAnalysis.cpp
index 489777f0..f5e3ed84 100644
--- a/src/base/SMPDataFlowAnalysis.cpp
+++ b/src/base/SMPDataFlowAnalysis.cpp
@@ -163,8 +163,8 @@ const char *SPARKFloatingPointStackRegNames[8] = { "FloatingPointStackDummy", "F
const char *CFTTypeStrings[20] = { "FALL_THROUGH", "BRANCH_IF_THEN", "BRANCH_IF_THEN_ELSE", "JUMP_BEFORE_ELSE",
"LOOP_BACK", "LOOP_EXIT", "JUMP_INTO_LOOP_TEST", "JUMP_TO_DEFAULT_CASE", "CASE_BREAK_TO_FOLLOW_NODE",
-"JUMP_TO_SWITCH_INDIR_JUMP", "SHORT_CIRCUIT_BRANCH", "SHORT_CIRCUIT_LOOP_EXIT", "INVERTED_LOOP_EXIT",
-"", "", "", "", "", "", ""
+"JUMP_TO_SWITCH_INDIR_JUMP", "SHORT_CIRCUIT_BRANCH", "SHORT_CIRCUIT_LOOP_EXIT", "INVERTED_LOOP_EXIT",
+"INVERTED_LOOP_BACK", "", "", "", "", "", ""
};
// Distinguishes subword regs from their parent regs
diff --git a/src/base/SMPFunction.cpp b/src/base/SMPFunction.cpp
index 8642815e..cf8599f5 100644
--- a/src/base/SMPFunction.cpp
+++ b/src/base/SMPFunction.cpp
@@ -12093,7 +12093,8 @@ int SMPFunction::TrackConditionalBranchTerminus(int BranchHeadBlockNum, int Curr
list<int> WorkListBlockNums;
STARS_ea_t LastAddr = CurrBlock->GetLastAddr();
ControlFlowType LastCFType = this->GetControlFlowType(LastAddr);
- if (LastCFType == LOOP_BACK) {
+ bool IsLoopBack = ((LastCFType == LOOP_BACK) || (LastCFType == INVERTED_LOOP_BACK));
+ if (IsLoopBack) {
// Don't follow back edge, but get the other successor, if conditional.
vector<SMPInstr *>::const_reverse_iterator LastInstIter = CurrBlock->GetRevInstCBegin();
if (COND_BRANCH == (*LastInstIter)->GetDataFlowType()) {
@@ -17014,7 +17015,12 @@ void SMPFunction::MarkSpecialNumericErrorCases(void) {
}
else if (CurrBlock->IsLoopTailBlock()) {
// We must be looping back to the loop header.
- this->SetControlFlowType(InstAddr, LOOP_BACK);
+ if (CurrBlock->HasInvertedLoopBack()) { // falling through to loop header
+ this->SetControlFlowType(InstAddr, INVERTED_LOOP_BACK);
+ }
+ else { // normal case; branching to loop header
+ this->SetControlFlowType(InstAddr, LOOP_BACK);
+ }
if (COND_BRANCH == CurrDataFlowType) {
int HeaderBlockNum = CurrBlock->GetLoopHeaderNumber();
if (!CurrBlock->IsDoubleLoopTailBlock()) { // normal case
@@ -23031,8 +23037,9 @@ void SMPFunction::EmitSPARKAdaForConditional(int HeaderBlockNum, int FollowBlock
// For the if-then case, we emit the code for the then-block and then "end if;" and return.
// For the if-then-else case, we emit the code for the then-block and then "else" etc.
ControlFlowType LastCFType = this->GetControlFlowType(LastAddr);
+ bool IsLoopBack = ((LastCFType == LOOP_BACK) || (LastCFType == INVERTED_LOOP_BACK));
bool StaysInLoop = this->IsNonExitingLoopBackBranch(LastAddr);
- bool IfThenCase = ((LastCFType == BRANCH_IF_THEN) || (StaysInLoop && ((LastCFType == LOOP_BACK) || (LastCFType == LOOP_EXIT))));
+ bool IfThenCase = ((LastCFType == BRANCH_IF_THEN) || (StaysInLoop && (IsLoopBack || (LastCFType == LOOP_EXIT))));
bool ShortCircuitCase = (LastCFType == SHORT_CIRCUIT_BRANCH);
assert(IfThenCase || ShortCircuitCase || (LastCFType == BRANCH_IF_THEN_ELSE));
int FallThroughBlockNum = SMP_BLOCKNUM_UNINIT;
@@ -23056,6 +23063,12 @@ void SMPFunction::EmitSPARKAdaForConditional(int HeaderBlockNum, int FollowBlock
assert(2 == HeaderBlock->GetNumSuccessors());
SuccIter = HeaderBlock->GetFallThroughSucc();
FallThroughBlockNum = (*SuccIter)->GetNumber();
+ if (LastCFType == INVERTED_LOOP_BACK) {
+ // Swap the fall-through and distant blocks.
+ int TempBlockNum = DistantBlockNum;
+ DistantBlockNum = FallThroughBlockNum;
+ FallThroughBlockNum = TempBlockNum;
+ }
}
SMPBasicBlock *ThenBlock = this->RPOBlocks[(size_t) FallThroughBlockNum];
bool CheckFTBlock = false; // check for falling out of loop?
diff --git a/src/base/SMPInstr.cpp b/src/base/SMPInstr.cpp
index 90b69a51..b94aa382 100644
--- a/src/base/SMPInstr.cpp
+++ b/src/base/SMPInstr.cpp
@@ -7014,7 +7014,7 @@ void SMPInstr::EmitSPARKAda(FILE *OutFile) {
; // jumps around else clauses are handled in SMPFunction::EmitSPARKAdaForConditional()
}
}
- else if (LOOP_BACK == FuncControlFlowType) {
+ else if ((LOOP_BACK == FuncControlFlowType) || (INVERTED_LOOP_BACK == FuncControlFlowType)) {
// We must be looping back to the loop header.
if (JUMP == CurrDataFlowType) { // simple case
#if STARS_SPARK_CENTRALIZE_EMIT_LOOP
--
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