[llvm] r306118 - [InlineCost] Do not take INT_MAX when Cost is negative

[Jun Bum Lim via llvm-commits]

Author: junbuml
Date: Fri Jun 23 11:12:37 2017
New Revision: 306118

URL: http://llvm.org/viewvc/llvm-project?rev=306118&view=rev
Log:
[InlineCost] Do not take INT_MAX when Cost is negative

Summary: visitSwitchInst should not take INT_MAX when Cost is negative. Instead of INT_MAX , we also use a valid upperbound cost when overflow occurs in Cost.

Reviewers: hans, echristo, dmgreen

Reviewed By: dmgreen

Subscribers: mcrosier, javed.absar, llvm-commits, eraman

Differential Revision: https://reviews.llvm.org/D34436

Modified:
    llvm/trunk/lib/Analysis/InlineCost.cpp
    llvm/trunk/test/Transforms/Inline/AArch64/switch.ll

Modified: llvm/trunk/lib/Analysis/InlineCost.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/InlineCost.cpp?rev=306118&r1=306117&r2=306118&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/InlineCost.cpp (original)
+++ llvm/trunk/lib/Analysis/InlineCost.cpp Fri Jun 23 11:12:37 2017
@@ -1022,12 +1022,15 @@ bool CallAnalyzer::visitSwitchInst(Switc
   // inlining those. It will prevent inlining in cases where the optimization
   // does not (yet) fire.
 
+  // Maximum valid cost increased in this function.
+  int CostUpperBound = INT_MAX - InlineConstants::InstrCost - 1;
+
   // Exit early for a large switch, assuming one case needs at least one
   // instruction.
   // FIXME: This is not true for a bit test, but ignore such case for now to
   // save compile-time.
   int64_t CostLowerBound =
-      std::min((int64_t)INT_MAX,
+      std::min((int64_t)CostUpperBound,
                (int64_t)SI.getNumCases() * InlineConstants::InstrCost + Cost);
 
   if (CostLowerBound > Threshold) {
@@ -1044,7 +1047,8 @@ bool CallAnalyzer::visitSwitchInst(Switc
   if (JumpTableSize) {
     int64_t JTCost = (int64_t)JumpTableSize * InlineConstants::InstrCost +
                      4 * InlineConstants::InstrCost;
-    Cost = std::min((int64_t)INT_MAX, JTCost + Cost);
+
+    Cost = std::min((int64_t)CostUpperBound, JTCost + Cost);
     return false;
   }
 
@@ -1068,10 +1072,12 @@ bool CallAnalyzer::visitSwitchInst(Switc
     Cost += NumCaseCluster * 2 * InlineConstants::InstrCost;
     return false;
   }
-  int64_t ExpectedNumberOfCompare = 3 * (uint64_t)NumCaseCluster / 2 - 1;
-  uint64_t SwitchCost =
+
+  int64_t ExpectedNumberOfCompare = 3 * (int64_t)NumCaseCluster / 2 - 1;
+  int64_t SwitchCost =
       ExpectedNumberOfCompare * 2 * InlineConstants::InstrCost;
-  Cost = std::min((uint64_t)INT_MAX, SwitchCost + Cost);
+
+  Cost = std::min((int64_t)CostUpperBound, SwitchCost + Cost);
   return false;
 }
 

Modified: llvm/trunk/test/Transforms/Inline/AArch64/switch.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/Inline/AArch64/switch.ll?rev=306118&r1=306117&r2=306118&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/Inline/AArch64/switch.ll (original)
+++ llvm/trunk/test/Transforms/Inline/AArch64/switch.ll Fri Jun 23 11:12:37 2017
@@ -121,3 +121,40 @@ define i32 @caller_jumptable(i32 %a, i32
   ret i32 %r
 }
 
+
+define internal i32 @callee_negativeCost(i32 %t)  {
+entry:
+  switch i32 %t, label %sw.default [
+    i32 1, label %sw.bb
+    i32 0, label %sw.bb1
+    i32 42, label %sw.bb2
+    i32 43, label %sw.bb3
+  ]
+
+sw.bb:                                            ; preds = %entry
+  br label %cleanup
+
+sw.bb1:                                           ; preds = %entry
+  br label %cleanup
+
+sw.bb2:                                           ; preds = %entry
+  br label %cleanup
+
+sw.bb3:                                           ; preds = %entry
+  br label %cleanup
+
+sw.default:                                       ; preds = %entry
+  br label %cleanup
+
+cleanup:                                          ; preds = %sw.default, %sw.bb3, %sw.bb2, %sw.bb1, %sw.bb
+  %retval.0 = phi i32 [ 1, %sw.default ], [ 3, %sw.bb3 ], [ 2, %sw.bb2 ], [ 0, %sw.bb1 ], [ 0, %sw.bb ]
+  ret i32 %retval.0
+}
+
+define i32 @caller_negativeCost(i32 %t) {
+; CHECK-LABEL: @caller_negativeCost(
+; CHECK-NOT: call i32 @callee_negativeCost
+entry:
+  %call = call i32 @callee_negativeCost(i32 %t)
+  ret i32 %call
+}