[llvm] r269791 - [Guards] Add branch metadata when lowering

[Sanjoy Das via llvm-commits]

Author: sanjoy
Date: Tue May 17 12:51:19 2016
New Revision: 269791

URL: http://llvm.org/viewvc/llvm-project?rev=269791&view=rev
Log:
[Guards] Add branch metadata when lowering

Guards are expected to basically never fail.  Reflect this in the branch
probabilities in their lowered form.

Modified:
    llvm/trunk/lib/Transforms/Scalar/LowerGuardIntrinsic.cpp
    llvm/trunk/test/Transforms/LowerGuardIntrinsic/basic.ll

Modified: llvm/trunk/lib/Transforms/Scalar/LowerGuardIntrinsic.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LowerGuardIntrinsic.cpp?rev=269791&r1=269790&r2=269791&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/LowerGuardIntrinsic.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/LowerGuardIntrinsic.cpp Tue May 17 12:51:19 2016
@@ -21,12 +21,18 @@
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/Intrinsics.h"
 #include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/MDBuilder.h"
 #include "llvm/IR/Module.h"
 #include "llvm/Pass.h"
 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
 
 using namespace llvm;
 
+static cl::opt<uint32_t> LikelyBranchWeight(
+    "guards-likely-branch-weight", cl::Hidden, cl::init(1 << 20),
+    cl::desc("The probability of a guard failing is assumed to be the "
+             "reciprocal of this value (default = 1 << 20)"));
+
 namespace {
 struct LowerGuardIntrinsic : public FunctionPass {
   static char ID;
@@ -59,6 +65,10 @@ static void MakeGuardControlFlowExplicit
   if (auto *MD = CI->getMetadata(LLVMContext::MD_make_implicit))
     CheckBI->setMetadata(LLVMContext::MD_make_implicit, MD);
 
+  MDBuilder MDB(CI->getContext());
+  CheckBI->setMetadata(LLVMContext::MD_prof,
+                       MDB.createBranchWeights(LikelyBranchWeight, 1));
+
   IRBuilder<> B(DeoptBlockTerm);
   auto *DeoptCall = B.CreateCall(DeoptIntrinsic, Args, {DeoptOB}, "");
 

Modified: llvm/trunk/test/Transforms/LowerGuardIntrinsic/basic.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LowerGuardIntrinsic/basic.ll?rev=269791&r1=269790&r2=269791&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/LowerGuardIntrinsic/basic.ll (original)
+++ llvm/trunk/test/Transforms/LowerGuardIntrinsic/basic.ll Tue May 17 12:51:19 2016
@@ -9,7 +9,7 @@ define i8 @f_basic(i1* %c_ptr) {
   call void(i1, ...) @llvm.experimental.guard(i1 %c, i32 1) [ "deopt"(i32 1) ]
   ret i8 5
 
-; CHECK:  br i1 %c, label %guarded, label %deopt
+; CHECK:  br i1 %c, label %guarded, label %deopt, !prof !0
 ; CHECK: deopt:
 ; CHECK-NEXT:  %deoptcall = call i8 (...) @llvm.experimental.deoptimize.i8(i32 1) [ "deopt"(i32 1) ]
 ; CHECK-NEXT:  ret i8 %deoptcall
@@ -24,7 +24,7 @@ define void @f_void_return_ty(i1* %c_ptr
   call void(i1, ...) @llvm.experimental.guard(i1 %c, i32 1) [ "deopt"() ]
   ret void
 
-; CHECK:  br i1 %c, label %guarded, label %deopt
+; CHECK:  br i1 %c, label %guarded, label %deopt, !prof !0
 ; CHECK: deopt:
 ; CHECK-NEXT:  call void (...) @llvm.experimental.deoptimize.isVoid(i32 1) [ "deopt"() ]
 ; CHECK-NEXT:  ret void
@@ -39,7 +39,7 @@ define void @f_multiple_args(i1* %c_ptr)
   call void(i1, ...) @llvm.experimental.guard(i1 %c, i32 1, i32 2, double 500.0) [ "deopt"(i32 2, i32 3) ]
   ret void
 
-; CHECK: br i1 %c, label %guarded, label %deopt
+; CHECK: br i1 %c, label %guarded, label %deopt, !prof !0
 ; CHECK: deopt:
 ; CHECK-NEXT:  call void (...) @llvm.experimental.deoptimize.isVoid(i32 1, i32 2, double 5.000000e+02) [ "deopt"(i32 2, i32 3) ]
 ; CHECK-NEXT:  ret void
@@ -53,7 +53,7 @@ define i32 @f_zero_args(i1* %c_ptr) {
   call void(i1, ...) @llvm.experimental.guard(i1 %c) [ "deopt"(i32 2, i32 3) ]
   ret i32 500
 
-; CHECK: br i1 %c, label %guarded, label %deopt
+; CHECK: br i1 %c, label %guarded, label %deopt, !prof !0
 ; CHECK: deopt:
 ; CHECK-NEXT:  %deoptcall = call i32 (...) @llvm.experimental.deoptimize.i32() [ "deopt"(i32 2, i32 3) ]
 ; CHECK-NEXT:  ret i32 %deoptcall
@@ -63,7 +63,7 @@ define i32 @f_zero_args(i1* %c_ptr) {
 
 define i8 @f_with_make_implicit_md(i32* %ptr) {
 ; CHECK-LABEL: @f_with_make_implicit_md(
-; CHECK:  br i1 %notNull, label %guarded, label %deopt, !make.implicit !0
+; CHECK:  br i1 %notNull, label %guarded, label %deopt, !prof !0, !make.implicit !1
 ; CHECK: deopt:
 ; CHECK-NEXT:  %deoptcall = call i8 (...) @llvm.experimental.deoptimize.i8(i32 1) [ "deopt"(i32 1) ]
 ; CHECK-NEXT:  ret i8 %deoptcall
@@ -72,3 +72,5 @@ define i8 @f_with_make_implicit_md(i32*
   call void(i1, ...) @llvm.experimental.guard(i1 %notNull, i32 1) [ "deopt"(i32 1) ], !make.implicit !{}
   ret i8 5
 }
+
+!0 = !{!"branch_weights", i32 1048576, i32 1}