[llvm] a63b5c9 - [CallSiteSplitting] Simplify isPredicateOnPHI & continue checking PHIs.

[Florian Hahn via llvm-commits]

Author: Florian Hahn
Date: 2020-04-02T10:11:27+01:00
New Revision: a63b5c9e53199b866b804164285a2c40531b31a1

URL: https://github.com/llvm/llvm-project/commit/a63b5c9e53199b866b804164285a2c40531b31a1
DIFF: https://github.com/llvm/llvm-project/commit/a63b5c9e53199b866b804164285a2c40531b31a1.diff

LOG: [CallSiteSplitting] Simplify isPredicateOnPHI & continue checking PHIs.

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().

Reviewers: davidxl, junbuml, thakis

Reviewed By: davidxl

Differential Revision: https://reviews.llvm.org/D77089

Added: 
    

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

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Scalar/CallSiteSplitting.cpp b/llvm/lib/Transforms/Scalar/CallSiteSplitting.cpp
index e34c011b1c87..286e237de1ea 100644
--- a/llvm/lib/Transforms/Scalar/CallSiteSplitting.cpp
+++ b/llvm/lib/Transforms/Scalar/CallSiteSplitting.cpp
@@ -424,22 +424,20 @@ static bool isPredicatedOnPHI(CallSite CS) {
   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;
 }

diff  --git a/llvm/test/Transforms/CallSiteSplitting/callsite-split-or-phi.ll b/llvm/test/Transforms/CallSiteSplitting/callsite-split-or-phi.ll
index cd2edb1e3355..83b265b14ed3 100644
--- a/llvm/test/Transforms/CallSiteSplitting/callsite-split-or-phi.ll
+++ b/llvm/test/Transforms/CallSiteSplitting/callsite-split-or-phi.ll
@@ -586,3 +586,37 @@ CallSiteBB:
 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
+}