add -bounds-checking-multiple-traps option to make one trap BB per check

disabled by default for now; we can discusse the default value (& name) later

llvm-svn: 157777

2 files changed, 17 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/Scalar/BoundsChecking.cpp b/llvm/lib/Transforms/Scalar/BoundsChecking.cpp
index 738b1f27bdb..2ed65ebbab1 100644
--- a/llvm/lib/Transforms/Scalar/BoundsChecking.cpp
+++ b/llvm/lib/Transforms/Scalar/BoundsChecking.cpp
@@ -20,6 +20,7 @@
 #include "llvm/Analysis/ScalarEvolution.h"
 #include "llvm/Analysis/ScalarEvolutionExpander.h"
 #include "llvm/Analysis/ScalarEvolutionExpressions.h"
+#include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/InstIterator.h"
 #include "llvm/Support/IRBuilder.h"
@@ -35,6 +36,9 @@
 #include "llvm/Pass.h"
 using namespace llvm;
 
+static cl::opt<bool> ManyTrapBB("bounds-checking-multiple-traps",
+                                cl::desc("Use one trap block per assertion"));
+
 STATISTIC(ChecksAdded, "Bounds checks added");
 STATISTIC(ChecksSkipped, "Bounds checks skipped");
 STATISTIC(ChecksUnable, "Bounds checks unable to add");
@@ -98,7 +102,7 @@ INITIALIZE_PASS_END(BoundsChecking, "bounds-checking",
 /// getTrapBB - create a basic block that traps. All overflowing conditions
 /// branch to this block. There's only one trap block per function.
 BasicBlock *BoundsChecking::getTrapBB() {
-  if (TrapBB)
+  if (TrapBB && !ManyTrapBB)
     return TrapBB;
 
   BasicBlock::iterator PrevInsertPoint = Builder->GetInsertPoint();
diff --git a/llvm/test/Transforms/BoundsChecking/many-trap.ll b/llvm/test/Transforms/BoundsChecking/many-trap.ll
new file mode 100644
index 00000000000..787779d1377
--- /dev/null
+++ b/llvm/test/Transforms/BoundsChecking/many-trap.ll
@@ -0,0 +1,12 @@
+; RUN: opt < %s -bounds-checking -bounds-checking-multiple-traps -S | FileCheck %s
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
+
+; CHECK: @f1
+define void @f1(i64 %x) nounwind {
+  %1 = alloca i128, i64 %x
+  %2 = load i128* %1, align 4
+  %3 = load i128* %1, align 4
+  ret void
+; CHECK: llvm.trap
+; CHECK: llvm.trap
+}