[llvm] r194346 - SimplifyCFG has a heuristics for out-of-order processors that decides when it is worthwhile to merge branches. It tries to estimate if the operands of the instruction that we want to hoist are ready. This commit marks function arguments as 'ready' because they require no calculation. This boosts libquantum and a few other workloads from the testsuite.

[Nadav Rotem]

Author: nadav
Date: Sat Nov  9 22:13:31 2013
New Revision: 194346

URL: http://llvm.org/viewvc/llvm-project?rev=194346&view=rev
Log:
SimplifyCFG has a heuristics for out-of-order processors that decides when it is worthwhile to merge branches. It tries to estimate if the operands of the instruction that we want to hoist are ready. This commit marks function arguments as 'ready' because they require no calculation. This boosts libquantum and a few other workloads from the testsuite.
  

Added:
    llvm/trunk/test/Transforms/SimplifyCFG/common-dest-folding.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=194346&r1=194345&r2=194346&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp Sat Nov  9 22:13:31 2013
@@ -2096,7 +2096,7 @@ bool llvm::FoldBranchToCommonDest(Branch
       for (Instruction::op_iterator OI = BonusInst->op_begin(),
            OE = BonusInst->op_end(); OI != OE; ++OI) {
         Value *V = *OI;
-        if (!isa<Constant>(V))
+        if (!isa<Constant>(V) && !isa<Argument>(V))
           UsedValues.insert(V);
       }
 

Added: llvm/trunk/test/Transforms/SimplifyCFG/common-dest-folding.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SimplifyCFG/common-dest-folding.ll?rev=194346&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/SimplifyCFG/common-dest-folding.ll (added)
+++ llvm/trunk/test/Transforms/SimplifyCFG/common-dest-folding.ll Sat Nov  9 22:13:31 2013
@@ -0,0 +1,28 @@
+; RUN: opt < %s -simplifycfg -S | FileCheck %s
+
+;CHECK: @foo
+;CHECK: and i32 %c1, %k
+;CHECK: icmp eq i32
+;CHECK: and i32 %c2, %k
+;CHECK: icmp eq i32
+;CHECK: or i1
+;CHECK: ret
+define i32 @foo(i32 %k, i32 %c1, i32 %c2) {
+  %1 = and i32 %c1, %k
+  %2 = icmp eq i32 %1, 0
+  br i1 %2, label %8, label %3
+
+; <label>:3                                       ; preds = %0
+  %4 = and i32 %c2, %k
+  %5 = icmp eq i32 %4, 0
+  br i1 %5, label %8, label %6
+
+; <label>:6                                       ; preds = %3
+  %7 = tail call i32 (...)* @bar() nounwind
+  br label %8
+
+; <label>:8                                       ; preds = %3, %0, %6
+  ret i32 undef
+}
+
+declare i32 @bar(...)