Elide boundscheck blocks when inbounds.

JuliaLang · Dec 23, 2015 · a6f6519 · a6f6519
1 parent 8ba1d6c
commit a6f6519
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Showing 2 changed files with 20 additions and 4 deletions.
diff --git a/src/cgutils.cpp b/src/cgutils.cpp
@@ -1332,12 +1332,21 @@ static void emit_typecheck(const jl_cgval_t &x, jl_value_t *type, const std::str
     builder.SetInsertPoint(passBB);
 }
 
+static bool is_inbounds(jl_codectx_t *ctx)
+{
+    // inbounds rule is either of top two values on inbounds stack are true
+    bool inbounds = !ctx->inbounds.empty() && ctx->inbounds.back();
+    if (ctx->inbounds.size() > 1)
+        inbounds ^= ctx->inbounds[ctx->inbounds.size()-2];
+    return inbounds;
+}
+
 #define CHECK_BOUNDS 1
 static Value *emit_bounds_check(const jl_cgval_t &ainfo, jl_value_t *ty, Value *i, Value *len, jl_codectx_t *ctx)
 {
     Value *im1 = builder.CreateSub(i, ConstantInt::get(T_size, 1));
 #if CHECK_BOUNDS==1
-    if (((ctx->boundsCheck.empty() || ctx->boundsCheck.back()==true) &&
+    if ((!is_inbounds(ctx) &&
          jl_options.check_bounds != JL_OPTIONS_CHECK_BOUNDS_OFF) ||
          jl_options.check_bounds == JL_OPTIONS_CHECK_BOUNDS_ON) {
         Value *ok = builder.CreateICmpULT(im1, len);
@@ -1842,7 +1851,7 @@ static Value *emit_array_nd_index(const jl_cgval_t &ainfo, jl_value_t *ex, size_
     Value *i = ConstantInt::get(T_size, 0);
     Value *stride = ConstantInt::get(T_size, 1);
 #if CHECK_BOUNDS==1
-    bool bc = ((ctx->boundsCheck.empty() || ctx->boundsCheck.back()==true) &&
+    bool bc = (!is_inbounds(ctx) &&
                jl_options.check_bounds != JL_OPTIONS_CHECK_BOUNDS_OFF) ||
         jl_options.check_bounds == JL_OPTIONS_CHECK_BOUNDS_ON;
     BasicBlock *failBB=NULL, *endBB=NULL;

diff --git a/src/codegen.cpp b/src/codegen.cpp
@@ -4432,8 +4432,8 @@ static void emit_function(jl_lambda_info_t *lam, jl_llvm_functions_t *declaratio
     ctx.funcName = jl_symbol_name(lam->name);
     ctx.vaName = NULL;
     ctx.vaStack = false;
-    // ctx.inbounds.push_back(false);
-    // ctx.boundsCheck.push_back(true);
+    ctx.inbounds.push_back(false);
+    ctx.boundsCheck.push_back(false);
     ctx.cyclectx = cyclectx;
 
     // step 2. process var-info lists to see what vars are captured, need boxing
@@ -5340,6 +5340,13 @@ static void emit_function(jl_lambda_info_t *lam, jl_llvm_functions_t *declaratio
                 builder.SetInsertPoint(bb);
             }
         }
+        // boundscheck elision
+        else if (is_inbounds(&ctx) && !ctx.boundsCheck.empty() && ctx.boundsCheck.back()) {
+            // skip expression unless it modifies the boundsCheck stack
+            if (jl_is_expr(stmt) && ((jl_expr_t*)stmt)->head == boundscheck_sym) {
+                (void)emit_expr(stmt, &ctx, false, false);
+            }
+        }
         else {
             (void)emit_expr(stmt, &ctx, false, false);
         }