Update discard mask pattern match fix

Update discard mask pattern match fix. Corrected predicate mode is set
for discard branch.

Author: lfilipko

IGC/Compiler/CISACodeGen/PatternMatchPass.cpp

@@ -3536,6 +3536,7 @@ bool CodeGenPatternMatch::MatchCanonicalizeInstruction(llvm::Instruction &I) {
 }
 
 bool CodeGenPatternMatch::MatchBranch(llvm::BranchInst &I) {
+  using namespace llvm::PatternMatch;
   struct CondBrInstPattern : Pattern {
     SSource cond;
     llvm::BranchInst *inst;
@@ -3553,9 +3554,24 @@ bool CodeGenPatternMatch::MatchBranch(llvm::BranchInst &I) {
   pattern->inst = &I;
 
   if (!I.isUnconditional()) {
+    Value *orSrc0 = nullptr;
+    Value *orSrc1 = nullptr;
     Value *cond = I.getCondition();
     if (dyn_cast<GenIntrinsicInst>(cond, GenISAIntrinsic::GenISA_UpdateDiscardMask)) {
       pattern->isDiscardBranch = true;
+    } else if (match(cond, m_Or(m_Value(orSrc0), m_Value(orSrc1)))) {
+      // %6 = call i1 @llvm.genx.GenISA.UpdateDiscardMask(i1 %0, i1 %2)
+      // %7 = or i1 %6, %2  (or: %7 = or i1 %2, %6)
+      // br i1 %7, label %DiscardRet, label %PostDiscard
+      if (auto intr = dyn_cast<GenIntrinsicInst>(orSrc0, GenISAIntrinsic::GenISA_UpdateDiscardMask)) {
+        if (intr->getOperand(1) == orSrc1) {
+          pattern->isDiscardBranch = true;
+        }
+      } else if (auto intr = dyn_cast<GenIntrinsicInst>(orSrc1, GenISAIntrinsic::GenISA_UpdateDiscardMask)) {
+        if (intr->getOperand(1) == orSrc0) {
+          pattern->isDiscardBranch = true;
+        }
+      }
     }
     pattern->cond = GetSource(I.getCondition(), false, false, IsSourceOfSample(&I));
   }