[PATCH] D86017: [BPI] Improve static heuristics for integer comparisons with CST

[Dávid Bolvanský via Phabricator via llvm-commits]

xbolva00 updated this revision to Diff 285945.
xbolva00 added a comment.

New logic


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D86017/new/

https://reviews.llvm.org/D86017

Files:
  llvm/lib/Analysis/BranchProbabilityInfo.cpp
  llvm/test/Analysis/BranchProbabilityInfo/integer_heuristics.ll


Index: llvm/test/Analysis/BranchProbabilityInfo/integer_heuristics.ll
===================================================================
--- llvm/test/Analysis/BranchProbabilityInfo/integer_heuristics.ll
+++ llvm/test/Analysis/BranchProbabilityInfo/integer_heuristics.ll
@@ -142,8 +142,8 @@
 entry: 
   %c = icmp ult i32 %x, %y
   br i1 %c, label %then, label %else
-; CHECK: edge entry -> then probability is 0x50000000 / 0x80000000 = 62.50%
-; CHECK: edge entry -> else probability is 0x30000000 / 0x80000000 = 37.50%
+; CHECK: edge entry -> then probability is 0x40000000 / 0x80000000 = 50.00%
+; CHECK: edge entry -> else probability is 0x40000000 / 0x80000000 = 50.00%
 then:
   br label %else
 ; CHECK: edge then -> else probability is 0x80000000 / 0x80000000 = 100.00% [HOT edge]
Index: llvm/lib/Analysis/BranchProbabilityInfo.cpp
===================================================================
--- llvm/lib/Analysis/BranchProbabilityInfo.cpp
+++ llvm/lib/Analysis/BranchProbabilityInfo.cpp
@@ -880,13 +880,17 @@
   Value *RHS = CI->getOperand(1);
   ConstantInt *CV = GetConstantInt(RHS);
   if (!CV) {
-    // X == Y -> Unlikely
-    // Otherwise -> Likely
-    if (CI->isTrueWhenEqual())
-      std::swap(TakenProb, UntakenProb);
-    setEdgeProbability(
-        BB, SmallVector<BranchProbability, 2>({TakenProb, UntakenProb}));
-    return true;
+    if (CI->isEquality()) {
+      // X == Y -> Unlikely
+      // X != Y -> Likely
+      if (CI->isTrueWhenEqual())
+        std::swap(TakenProb, UntakenProb);
+      setEdgeProbability(
+          BB, SmallVector<BranchProbability, 2>({TakenProb, UntakenProb}));
+      return true;
+    } else {
+      return false;
+    }
   }
 
   // If the LHS is the result of AND'ing a value with a single bit bitmask,
@@ -928,16 +932,12 @@
     default:
       return false;
     }
+  } else if (CI->isEquality()) {
+    // X == C -> Unlikely
+    // X != C -> Likely
+    isProb = !CI->isTrueWhenEqual();
   } else if (CV->isZero()) {
     switch (CI->getPredicate()) {
-    case CmpInst::ICMP_EQ:
-      // X == 0   ->  Unlikely
-      isProb = false;
-      break;
-    case CmpInst::ICMP_NE:
-      // X != 0   ->  Likely
-      isProb = true;
-      break;
     case CmpInst::ICMP_SLT:
       // X < 0   ->  Unlikely
       isProb = false;
@@ -958,14 +958,6 @@
       return false;
   } else if (CV->isMinusOne()) {
     switch (CI->getPredicate()) {
-    case CmpInst::ICMP_EQ:
-      // X == -1  ->  Unlikely
-      isProb = false;
-      break;
-    case CmpInst::ICMP_NE:
-      // X != -1  ->  Likely
-      isProb = true;
-      break;
     case CmpInst::ICMP_SGT:
       // InstCombine canonicalizes X >= 0 into X > -1.
       // X >= 0   ->  Likely
@@ -975,18 +967,7 @@
       return false;
     }
   } else {
-    // X == C -> Unlikely
-    // X != C -> Likely
-    switch (CI->getPredicate()) {
-    case CmpInst::ICMP_EQ:
-      isProb = false;
-      break;
-    case CmpInst::ICMP_NE:
-      isProb = true;
-      break;
-    default:
-      return false;
-    }
+    return false;
   }
 
   if (!isProb)


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