Merge pull request #856 from jbrodman/master

Fix issue where break stmts would in executing with mask all off.

ctx.cpp

@@ -741,6 +741,7 @@ FunctionEmitContext::Break(bool doCoherenceCheck) {
         // that have executed a 'break' statement:
         // breakLanes = breakLanes | mask
         AssertPos(currentPos, breakLanesPtr != NULL);
+
         llvm::Value *mask = GetInternalMask();
         llvm::Value *breakMask = LoadInst(breakLanesPtr,
                                           "break_mask");
@@ -879,7 +880,7 @@ FunctionEmitContext::jumpIfAllLoopLanesAreDone(llvm::BasicBlock *target) {
             finishedLanes = BinaryOperator(llvm::Instruction::Or, finishedLanes,
                                            continued, "returned|breaked|continued");
         }
-        
+          
         finishedLanes = BinaryOperator(llvm::Instruction::And,
                                        finishedLanes, GetFunctionMask(),
                                        "finished&func");
@@ -923,6 +924,16 @@ FunctionEmitContext::RestoreContinuedLanes() {
 }
 
 
+void
+FunctionEmitContext::ClearBreakLanes() {
+  if (breakLanesPtr == NULL)
+    return;
+
+  // breakLanes = 0
+  StoreInst(LLVMMaskAllOff, breakLanesPtr);
+}
+
+
 void
 FunctionEmitContext::StartSwitch(bool cfIsUniform, llvm::BasicBlock *bbBreak) {
     llvm::Value *oldMask = GetInternalMask();

ctx.h

@@ -195,6 +195,13 @@ public:
         'continue' statement when going through the loop body in the
         previous iteration. */
     void RestoreContinuedLanes();
+    
+    /** This method is called by code emitting IR for a loop.  It clears 
+        any lanes that contained a break since the mask has been updated to take
+        them into account.  This is necessary as all the bail out checks for 
+        breaks are meant to only deal with lanes breaking on the current iteration.
+     */
+    void ClearBreakLanes();
 
     /** Indicates that code generation for a "switch" statement is about to
         start.  isUniform indicates whether the "switch" value is uniform,

stmt.cpp

@@ -532,7 +532,6 @@ IfStmt::emitMaskedTrueAndFalse(FunctionEmitContext *ctx, llvm::Value *oldMask,
     }
 }
 
-
 /** Emit code for an if test that checks the mask and the test values and
     tries to be smart about jumping over code that doesn't need to be run.
  */
@@ -902,8 +901,10 @@ void DoStmt::EmitCode(FunctionEmitContext *ctx) const {
     // the code for the test.  This is only necessary for varying loops;
     // 'uniform' loops just jump when they hit a continue statement and
     // don't mess with the mask.
-    if (!uniformTest)
+    if (!uniformTest) {
         ctx->RestoreContinuedLanes();
+        ctx->ClearBreakLanes();
+    }
     llvm::Value *testValue = testExpr->GetValue(ctx);
     if (!testValue)
         return;
@@ -1111,6 +1112,8 @@ ForStmt::EmitCode(FunctionEmitContext *ctx) const {
     // test code.
     ctx->SetCurrentBasicBlock(bstep);
     ctx->RestoreContinuedLanes();
+    ctx->ClearBreakLanes();
+
     if (step)
         step->EmitCode(ctx);
     ctx->BranchInst(btest);