[llvm-commits] [llvm] r124826 - in /llvm/trunk: lib/Transforms/Utils/SimplifyCFG.cpp test/Transforms/SimplifyCFG/switch-to-icmp.ll

[Benjamin Kramer]

Author: d0k
Date: Thu Feb  3 16:51:41 2011
New Revision: 124826

URL: http://llvm.org/viewvc/llvm-project?rev=124826&view=rev
Log:
SimplifyCFG: Also transform switches that represent a range comparison but are not sorted into sub+icmp.

This transforms another 1000 switches in gcc.c.

Added:
    llvm/trunk/test/Transforms/SimplifyCFG/switch-to-icmp.ll
Modified:
    llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp

Modified: llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp?rev=124826&r1=124825&r2=124826&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp Thu Feb  3 16:51:41 2011
@@ -2241,14 +2241,25 @@
 /// integer range comparison into a sub, an icmp and a branch.
 static bool TurnSwitchRangeIntoICmp(SwitchInst *SI) {
   assert(SI->getNumCases() > 2 && "Degenerate switch?");
-  // We can do this transform if the switch consists of an ascending series
-  // and all cases point to the same destination.
-  for (unsigned I = 2, E = SI->getNumCases(); I != E; ++I)
-    if (SI->getSuccessor(I-1) != SI->getSuccessor(I) ||
-        SI->getCaseValue(I-1)->getValue()+1 != SI->getCaseValue(I)->getValue())
+
+  // Make sure all cases point to the same destination and gather the values.
+  SmallVector<ConstantInt *, 16> Cases;
+  Cases.push_back(SI->getCaseValue(1));
+  for (unsigned I = 2, E = SI->getNumCases(); I != E; ++I) {
+    if (SI->getSuccessor(I-1) != SI->getSuccessor(I))
       return false;
+    Cases.push_back(SI->getCaseValue(I));
+  }
+  assert(Cases.size() == SI->getNumCases()-1 && "Not all cases gathered");
+
+  // Sort the case values, then check if they form a range we can transform.
+  array_pod_sort(Cases.begin(), Cases.end(), ConstantIntSortPredicate);
+  for (unsigned I = 1, E = Cases.size(); I != E; ++I) {
+    if (Cases[I-1]->getValue() != Cases[I]->getValue()+1)
+      return false;
+  }
 
-  Constant *Offset = ConstantExpr::getNeg(SI->getCaseValue(1));
+  Constant *Offset = ConstantExpr::getNeg(Cases.back());
   Constant *NumCases = ConstantInt::get(Offset->getType(), SI->getNumCases()-1);
 
   Value *Sub = BinaryOperator::CreateAdd(SI->getCondition(), Offset, "off", SI);

Added: llvm/trunk/test/Transforms/SimplifyCFG/switch-to-icmp.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SimplifyCFG/switch-to-icmp.ll?rev=124826&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/SimplifyCFG/switch-to-icmp.ll (added)
+++ llvm/trunk/test/Transforms/SimplifyCFG/switch-to-icmp.ll Thu Feb  3 16:51:41 2011
@@ -0,0 +1,40 @@
+; RUN: opt -S -simplifycfg < %s | FileCheck %s
+
+define zeroext i1 @test1(i32 %x) nounwind readnone ssp noredzone {
+entry:
+ switch i32 %x, label %lor.rhs [
+   i32 2, label %lor.end
+   i32 1, label %lor.end
+   i32 3, label %lor.end
+ ]
+
+lor.rhs:
+ br label %lor.end
+
+lor.end:
+ %0 = phi i1 [ true, %entry ], [ false, %lor.rhs ], [ true, %entry ], [ true, %entry ]
+ ret i1 %0
+
+; CHECK: @test1
+; CHECK: %off = add i32 %x, -1
+; CHECK: %switch = icmp ult i32 %off, 3
+}
+
+define zeroext i1 @test2(i32 %x) nounwind readnone ssp noredzone {
+entry:
+ switch i32 %x, label %lor.rhs [
+   i32 0, label %lor.end
+   i32 1, label %lor.end
+ ]
+
+lor.rhs:
+ br label %lor.end
+
+lor.end:
+ %0 = phi i1 [ true, %entry ], [ false, %lor.rhs ], [ true, %entry ]
+ ret i1 %0
+
+; CHECK: @test2
+; CHECK: %off = add i32 %x, 0
+; CHECK: %switch = icmp ult i32 %off, 2
+}