Allow unsigned comparisons

  With this patch we will optimistically assume that the result of an unsigned
  comparison is the same as the result of the same comparison interpreted as
  signed.

llvm-svn: 267559

3 files changed, 12 insertions, 28 deletions

diff --git a/polly/lib/Analysis/ScopDetection.cpp b/polly/lib/Analysis/ScopDetection.cpp
index 2e1caf51b10..4ee92fcfa93 100644
--- a/polly/lib/Analysis/ScopDetection.cpp
+++ b/polly/lib/Analysis/ScopDetection.cpp
@@ -149,11 +149,6 @@ static cl::opt<bool>
                            cl::Hidden, cl::init(false), cl::ZeroOrMore,
                            cl::cat(PollyCategory));
 
-static cl::opt<bool> AllowUnsigned("polly-allow-unsigned",
-                                   cl::desc("Allow unsigned expressions"),
-                                   cl::Hidden, cl::init(false), cl::ZeroOrMore,
-                                   cl::cat(PollyCategory));
-
 static cl::opt<bool, true>
     TrackFailures("polly-detect-track-failures",
                   cl::desc("Track failure strings in detecting scop regions"),
@@ -385,13 +380,6 @@ bool ScopDetection::isValidBranch(BasicBlock &BB, BranchInst *BI,
   }
 
   ICmpInst *ICmp = cast<ICmpInst>(Condition);
-  // Unsigned comparisons are not allowed. They trigger overflow problems
-  // in the code generation.
-  //
-  // TODO: This is not sufficient and just hides bugs. However it does pretty
-  //       well.
-  if (ICmp->isUnsigned() && !AllowUnsigned)
-    return invalid<ReportUnsignedCond>(Context, /*Assert=*/true, BI, &BB);
 
   // Are both operands of the ICmp affine?
   if (isa<UndefValue>(ICmp->getOperand(0)) ||
diff --git a/polly/lib/Analysis/ScopDetectionDiagnostic.cpp b/polly/lib/Analysis/ScopDetectionDiagnostic.cpp
index 5d5a1a43f8e..25b121bc3ae 100644
--- a/polly/lib/Analysis/ScopDetectionDiagnostic.cpp
+++ b/polly/lib/Analysis/ScopDetectionDiagnostic.cpp
@@ -196,22 +196,6 @@ bool ReportInvalidCond::classof(const RejectReason *RR) {
 }
 
 //===----------------------------------------------------------------------===//
-// ReportUnsignedCond.
-
-std::string ReportUnsignedCond::getMessage() const {
-  return ("Condition in BB '" + BB->getName()).str() +
-         "' performs a comparision on (not yet supported) unsigned integers.";
-}
-
-std::string ReportUnsignedCond::getEndUserMessage() const {
-  return "Unsupported comparision on unsigned integers encountered";
-}
-
-bool ReportUnsignedCond::classof(const RejectReason *RR) {
-  return RR->getKind() == rrkUnsignedCond;
-}
-
-//===----------------------------------------------------------------------===//
 // ReportUndefOperand.
 
 std::string ReportUndefOperand::getMessage() const {
diff --git a/polly/lib/Analysis/ScopInfo.cpp b/polly/lib/Analysis/ScopInfo.cpp
index 3b8770afa9a..014919634ed 100644
--- a/polly/lib/Analysis/ScopInfo.cpp
+++ b/polly/lib/Analysis/ScopInfo.cpp
@@ -1317,6 +1317,18 @@ buildConditionSets(ScopStmt &Stmt, Value *Condition, TerminatorInst *TI,
     isl_pw_aff *LHS, *RHS;
     LHS = Stmt.getPwAff(SE.getSCEVAtScope(ICond->getOperand(0), L));
     RHS = Stmt.getPwAff(SE.getSCEVAtScope(ICond->getOperand(1), L));
+
+    if (ICond->isUnsigned()) {
+      // For unsigned comparisons we assumed the signed bit of neither operand
+      // to be set. The comparison is equal to a signed comparison under this
+      // assumption.
+      auto *BB = Stmt.getEntryBlock();
+      S.recordAssumption(UNSIGNED, isl_pw_aff_nonneg_set(isl_pw_aff_copy(LHS)),
+                         TI->getDebugLoc(), AS_ASSUMPTION, BB);
+      S.recordAssumption(UNSIGNED, isl_pw_aff_nonneg_set(isl_pw_aff_copy(RHS)),
+                         TI->getDebugLoc(), AS_ASSUMPTION, BB);
+    }
+
     ConsequenceCondSet =
         buildConditionSet(ICond->getPredicate(), LHS, RHS, Domain);
   }