[InstCombine] Add a DEBUG_COUNTER to InstCombine to limit how many instructions are...

Sometimes it would be nice to stop InstCombine mid way through its combining to see the current IR. By using a debug counter we can place an upper limit on how many instructions to process.

This will also allow skipping the first X combines, but that has the potential to change later combines since earlier canonicalizations might have been skipped.

Differential Revision: https://reviews.llvm.org/D36553

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@310638 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/InstCombine/InstructionCombining.cpp b/lib/Transforms/InstCombine/InstructionCombining.cpp
index 4b542d77d183035021e79ca0c73627220c9b442b..b07e2cc2d2a02a5969ada63fe956936cf9e06cef 100644 (file)
--- a/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -60,6 +60,7 @@
 #include "llvm/IR/ValueHandle.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
+#include "llvm/Support/DebugCounter.h"
 #include "llvm/Support/KnownBits.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Transforms/InstCombine/InstCombine.h"
@@ -79,6 +80,8 @@ STATISTIC(NumSunkInst , "Number of instructions sunk");
 STATISTIC(NumExpand,    "Number of expansions");
 STATISTIC(NumFactor   , "Number of factorizations");
 STATISTIC(NumReassoc  , "Number of reassociations");
+DEBUG_COUNTER(VisitCounter, "instcombine-visit",
+              "Controls which instructions are visited");
 
 static cl::opt<bool>
 EnableExpensiveCombines("expensive-combines",
@@ -2882,6 +2885,9 @@ bool InstCombiner::run() {
       continue;
     }
 
+    if (!DebugCounter::shouldExecute(VisitCounter))
+      continue;
+
     // Instruction isn't dead, see if we can constant propagate it.
     if (!I->use_empty() &&
         (I->getNumOperands() == 0 || isa<Constant>(I->getOperand(0)))) {