[PATCH] D77089: [CallSiteSplitting] Simplify isPredicateOnPHI & continue checking PHIs.

[Florian Hahn via Phabricator via llvm-commits]

fhahn created this revision.
fhahn added reviewers: davidxl, junbuml, thakis.
Herald added a subscriber: hiraditya.
Herald added a project: LLVM.

As pointed out by @thakis, currently CallSiteSplitting bails out after
checking the first PHI node. We should check all PHI nodes, until we
find one where call site splitting is beneficial.

This patch also slightly simplifies the code using BasicBlock::phis().


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D77089

Files:
  llvm/lib/Transforms/Scalar/CallSiteSplitting.cpp
  llvm/test/Transforms/CallSiteSplitting/callsite-split-or-phi.ll


Index: llvm/test/Transforms/CallSiteSplitting/callsite-split-or-phi.ll
===================================================================
--- llvm/test/Transforms/CallSiteSplitting/callsite-split-or-phi.ll
+++ llvm/test/Transforms/CallSiteSplitting/callsite-split-or-phi.ll
@@ -586,3 +586,37 @@
 End:
   ret void
 }
+
+; CHECK-LABEL: i32 @test_multiple_phis(
+; CHECK:      Header.split:
+; CHECK-NEXT:   %r2 = call i32 @callee(i32* null, i32 1, i32 5)
+; CHECK-NEXT:   br label %Tail
+
+; CHECK:      TBB.split:
+; CHECK-NEXT:   %r1 = call i32 @callee(i32* null, i32 2, i32 10)
+; CHECK-NEXT:   br label %Tail
+
+; CHECK:        Tail:
+; CHECK-NEXT:   %phi.call = phi i32 [ %r1, %TBB.split ], [ %r2, %Header.split ]
+; CHECK-NEXT:   %p.0 = phi i32 [ 0, %Header.split ], [ 99, %TBB.split ]
+; CHECK-NEXT:   %res = add i32 %phi.call, %p.0
+; CHECK-NEXT:   ret i32 %phi.call
+;
+define i32 @test_multiple_phis(i1 %c.1) {
+Header:
+  br i1 %c.1, label %Tail, label %TBB
+
+TBB:
+  br label %Tail
+
+Tail:
+  %p.0 = phi i32 [0, %Header], [99, %TBB]
+  %p.1 = phi i32[1, %Header], [2, %TBB]
+  %p.2 = phi i32 [5, %Header], [10, %TBB]
+  %r = call i32 @callee(i32* null, i32 %p.1, i32 %p.2)
+  %res = add i32 %r, %p.0
+  ret i32 %r
+
+End:
+  ret i32 10
+}
Index: llvm/lib/Transforms/Scalar/CallSiteSplitting.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/CallSiteSplitting.cpp
+++ llvm/lib/Transforms/Scalar/CallSiteSplitting.cpp
@@ -424,22 +424,20 @@
   if (Instr != Parent->getFirstNonPHIOrDbg())
     return false;
 
-  for (auto &BI : *Parent) {
-    if (PHINode *PN = dyn_cast<PHINode>(&BI)) {
-      for (auto &I : CS.args())
-        if (&*I == PN) {
-          assert(PN->getNumIncomingValues() == 2 &&
-                 "Unexpected number of incoming values");
-          if (PN->getIncomingBlock(0) == PN->getIncomingBlock(1))
-            return false;
-          if (PN->getIncomingValue(0) == PN->getIncomingValue(1))
-            continue;
-          if (isa<Constant>(PN->getIncomingValue(0)) &&
-              isa<Constant>(PN->getIncomingValue(1)))
-            return true;
-        }
+  for (auto &PN : Parent->phis()) {
+    for (auto &Arg : CS.args()) {
+      if (&*Arg != &PN)
+        continue;
+      assert(PN.getNumIncomingValues() == 2 &&
+             "Unexpected number of incoming values");
+      if (PN.getIncomingBlock(0) == PN.getIncomingBlock(1))
+        return false;
+      if (PN.getIncomingValue(0) == PN.getIncomingValue(1))
+        continue;
+      if (isa<Constant>(PN.getIncomingValue(0)) &&
+          isa<Constant>(PN.getIncomingValue(1)))
+        return true;
     }
-    break;
   }
   return false;
 }


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