[CVP] Handle minmax at use

llvm · Feb 1, 2025 · 1cd00ec · 1cd00ec
1 parent fc520e8
commit 1cd00ec
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Showing 2 changed files with 37 additions and 3 deletions.
diff --git a/llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp b/llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
@@ -610,7 +610,42 @@ static bool processMinMaxIntrinsic(MinMaxIntrinsic *MM, LazyValueInfo *LVI) {
     return true;
   }
 
-  return false;
+  bool Changed = false;
+  for (Use &U : make_early_inc_range(MM->uses())) {
+    ConstantRange LHS_CR =
+        ConstantRange::getEmpty(MM->getType()->getScalarSizeInBits());
+    ConstantRange RHS_CR = LHS_CR;
+    auto *CxtI = cast<Instruction>(U.getUser());
+    if (auto *PN = dyn_cast<PHINode>(CxtI)) {
+      BasicBlock *FromBB = PN->getIncomingBlock(U);
+      LHS_CR = LVI->getConstantRangeOnEdge(MM->getOperand(0), FromBB,
+                                           CxtI->getParent(), CxtI);
+      RHS_CR = LVI->getConstantRangeOnEdge(MM->getOperand(1), FromBB,
+                                           CxtI->getParent(), CxtI);
+    } else {
+      LHS_CR = LVI->getConstantRange(MM->getOperand(0), CxtI,
+                                     /*UndefAllowed=*/false);
+      RHS_CR = LVI->getConstantRange(MM->getOperand(1), CxtI,
+                                     /*UndefAllowed=*/false);
+    }
+    if (LHS_CR.icmp(Pred, RHS_CR)) {
+      Changed = true;
+      ++NumMinMax;
+      U.set(MM->getLHS());
+      continue;
+    }
+    if (RHS_CR.icmp(Pred, LHS_CR)) {
+      Changed = true;
+      ++NumMinMax;
+      U.set(MM->getRHS());
+      continue;
+    }
+  }
+
+  if (MM->use_empty())
+    MM->eraseFromParent();
+
+  return Changed;
 }
 
 // Rewrite this with.overflow intrinsic as non-overflowing.

diff --git a/llvm/test/Transforms/CorrelatedValuePropagation/min-max.ll b/llvm/test/Transforms/CorrelatedValuePropagation/min-max.ll
@@ -360,10 +360,9 @@ define i64 @test_at_use2(i32 %x) {
 ; CHECK-LABEL: @test_at_use2(
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[COND:%.*]] = icmp slt i32 [[X:%.*]], 0
-; CHECK-NEXT:    [[SMAX:%.*]] = call i32 @llvm.smax.i32(i32 [[X]], i32 -1)
 ; CHECK-NEXT:    br i1 [[COND]], label [[IF_END:%.*]], label [[IF_THEN:%.*]]
 ; CHECK:       if.then:
-; CHECK-NEXT:    [[EXT:%.*]] = zext nneg i32 [[SMAX]] to i64
+; CHECK-NEXT:    [[EXT:%.*]] = zext nneg i32 [[X]] to i64
 ; CHECK-NEXT:    ret i64 [[EXT]]
 ; CHECK:       if.end:
 ; CHECK-NEXT:    ret i64 0