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

diff --git a/polly/include/polly/ScopDetectionDiagnostic.h b/polly/include/polly/ScopDetectionDiagnostic.h
index 4f16a1c..6db8096 100644 (file)
--- a/polly/include/polly/ScopDetectionDiagnostic.h
+++ b/polly/include/polly/ScopDetectionDiagnostic.h
@@ -68,7 +68,6 @@ enum RejectReasonKind {
   rrkAffFunc,
   rrkUndefCond,
   rrkInvalidCond,
-  rrkUnsignedCond,
   rrkUndefOperand,
   rrkNonAffBranch,
   rrkNoBasePtr,
@@ -346,32 +345,6 @@ public:
 };
 
 //===----------------------------------------------------------------------===//
-/// @brief Captures an condition on unsigned values
-///
-/// We do not yet allow conditions on unsigend values
-class ReportUnsignedCond : public ReportAffFunc {
-  //===--------------------------------------------------------------------===//
-
-  // The BasicBlock we found the broken condition in.
-  BasicBlock *BB;
-
-public:
-  ReportUnsignedCond(const Instruction *Inst, BasicBlock *BB)
-      : ReportAffFunc(rrkUnsignedCond, Inst), BB(BB) {}
-
-  /// @name LLVM-RTTI interface
-  //@{
-  static bool classof(const RejectReason *RR);
-  //@}
-
-  /// @name RejectReason interface
-  //@{
-  virtual std::string getMessage() const override;
-  virtual std::string getEndUserMessage() const override;
-  //@}
-};
-
-//===----------------------------------------------------------------------===//
 /// @brief Captures an undefined operand.
 class ReportUndefOperand : public ReportAffFunc {
   //===--------------------------------------------------------------------===//

diff --git a/polly/lib/Analysis/ScopDetection.cpp b/polly/lib/Analysis/ScopDetection.cpp
index 2e1caf5..4ee92fc 100644 (file)
--- 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 5d5a1a4..25b121b 100644 (file)
--- 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 3b8770a..0149196 100644 (file)
--- 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);
   }

diff --git a/polly/test/ScopInfo/simple_loop_unsigned.ll b/polly/test/ScopInfo/simple_loop_unsigned.ll
new file mode 100644 (file)
index 0000000..0f451f2
--- /dev/null
+++ b/polly/test/ScopInfo/simple_loop_unsigned.ll
@@ -0,0 +1,32 @@
+; RUN: opt %loadPolly -polly-scops -analyze < %s | FileCheck %s
+
+; void f(int a[], unsigned N) {
+;   unsigned i;
+;   do {
+;     a[i] = i;
+;   } while (++i <= N);
+; }
+
+; CHECK:      Assumed Context:
+; CHECK-NEXT: [N] -> {  : N >= 0 }
+;
+; CHECK:              Domain :=
+; CHECK-NEXT:             [N] -> { Stmt_bb[i0] : 0 <= i0 < N; Stmt_bb[0] : N <= 0 };
+
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128"
+
+define void @f(i64* nocapture %a, i64 %N) nounwind {
+entry:
+  br label %bb
+
+bb:                                               ; preds = %bb, %entry
+  %i = phi i64 [ 0, %entry ], [ %i.inc, %bb ]
+  %scevgep = getelementptr inbounds i64, i64* %a, i64 %i
+  store i64 %i, i64* %scevgep
+  %i.inc = add nsw i64 %i, 1
+  %exitcond = icmp uge i64 %i.inc, %N
+  br i1 %exitcond, label %return, label %bb
+
+return:                                           ; preds = %bb, %entry
+  ret void
+}

diff --git a/polly/test/ScopInfo/simple_loop_unsigned_2.ll b/polly/test/ScopInfo/simple_loop_unsigned_2.ll
new file mode 100644 (file)
index 0000000..744bf27
--- /dev/null
+++ b/polly/test/ScopInfo/simple_loop_unsigned_2.ll
@@ -0,0 +1,25 @@
+; RUN: opt %loadPolly -polly-scops -analyze < %s | FileCheck %s
+
+; CHECK:      Assumed Context:
+; CHECK-NEXT: [N] -> {  : N > 0 }
+;
+; CHECK:              Domain :=
+; CHECK-NEXT:             [N] -> { Stmt_bb[i0] : 0 <= i0 < N; Stmt_bb[0] : N <= 0 };
+;
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128"
+
+define void @f(i64* nocapture %a, i64 %N) nounwind {
+entry:
+  br label %bb
+
+bb:                                               ; preds = %bb, %entry
+  %i = phi i64 [ %N, %entry ], [ %i.dec, %bb ]
+  %scevgep = getelementptr inbounds i64, i64* %a, i64 %i
+  store i64 %i, i64* %scevgep
+  %i.dec = add nsw i64 %i, -1
+  %exitcond = icmp ugt i64 %i.dec, 0
+  br i1 %exitcond, label %bb, label %return
+
+return:                                           ; preds = %bb, %entry
+  ret void
+}

diff --git a/polly/test/ScopInfo/simple_loop_unsigned_3.ll b/polly/test/ScopInfo/simple_loop_unsigned_3.ll
new file mode 100644 (file)
index 0000000..d495b68
--- /dev/null
+++ b/polly/test/ScopInfo/simple_loop_unsigned_3.ll
@@ -0,0 +1,26 @@
+; RUN: opt %loadPolly -polly-scops -analyze < %s | FileCheck %s
+
+; CHECK:      Assumed Context:
+; CHECK-NEXT: [N] -> { : }
+;
+; CHECK:              Domain :=
+; CHECK-NEXT:             [N] -> { Stmt_bb[i0] : 0 < i0 <= 1000 - N; Stmt_bb[0] };
+
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128"
+
+define void @f(i64* nocapture %a, i64 %N) nounwind {
+entry:
+  br label %bb
+
+bb:                                               ; preds = %bb, %entry
+  %i = phi i64 [ 1000, %entry ], [ %i.dec, %bb ]
+  %scevgep = getelementptr inbounds i64, i64* %a, i64 %i
+  store i64 %i, i64* %scevgep
+  %i.dec = add nsw i64 %i, -1
+  %sub = sub nsw i64 %N, %i
+  %exitcond = icmp ult i64 %sub, 0
+  br i1 %exitcond, label %bb, label %return
+
+return:                                           ; preds = %bb, %entry
+  ret void
+}

diff --git a/polly/test/ScopInfo/unsigned-condition.ll b/polly/test/ScopInfo/unsigned-condition.ll
index 69c815e..57c1039 100644 (file)
--- a/polly/test/ScopInfo/unsigned-condition.ll
+++ b/polly/test/ScopInfo/unsigned-condition.ll
@@ -1,4 +1,4 @@
-; RUN: opt %loadPolly -polly-scops -analyze -polly-allow-unsigned < %s | FileCheck %s
+; RUN: opt %loadPolly -polly-scops -analyze < %s | FileCheck %s
 
 ; void f(int a[], int N, unsigned P) {
 ;   int i;
@@ -7,6 +7,17 @@
 ;       a[i] = i;
 ; }
 
+; The assumed context is the universe because the "signed-unsigned assumption"
+;   [P, N] -> {  : N > 0 and P >= 0 }
+; is implied by the execution domain. Thus if something is executed this
+; assumption will hold.
+
+; CHECK:      Assumed Context:
+; CHECK-NEXT: [P, N] -> {  :  }
+;
+; CHECK:              Domain :=
+; CHECK-NEXT:             [P, N] -> { Stmt_store[i0] : P >= 42 and 0 <= i0 < N };
+
 target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128"
 
 define void @f(i64* nocapture %a, i64 %N, i64 %P) nounwind {
@@ -31,17 +42,3 @@ bb.backedge:
 return:
   ret void
 }
-
-
-; CHECK:      Assumed Context:
-; CHECK-NEXT: [P, N] -> {  :  }
-;
-; CHECK:      Statements {
-; CHECK-NEXT:     Stmt_store
-; CHECK-NEXT:         Domain :=
-; CHECK-NEXT:             [P, N] -> { Stmt_store[i0] : P >= 42 and 0 <= i0 < N };
-; CHECK-NEXT:         Schedule :=
-; CHECK-NEXT:             [P, N] -> { Stmt_store[i0] -> [i0] };
-; CHECK-NEXT:         MustWriteAccess :=    [Reduction Type: NONE] [Scalar: 0]
-; CHECK-NEXT:             [P, N] -> { Stmt_store[i0] -> MemRef_a[i0] };
-; CHECK-NEXT: }