From 1ff08e389f82561659945bab8a55bdba5fc8e9dc Mon Sep 17 00:00:00 2001
From: "Duncan P. N. Exon Smith" <dexonsmith@apple.com>
Date: Sun, 2 Feb 2014 22:43:55 +0000
Subject: [PATCH] Lower llvm.expect intrinsic correctly for i1

LowerExpectIntrinsic previously only understood the idiom of an expect
intrinsic followed by a comparison with zero. For llvm.expect.i1, the
comparison would be stripped by the early-cse pass.

Patch by Daniel Micay.

llvm-svn: 200664
---
 llvm/docs/LangRef.rst                         |  4 +++
 .../Transforms/Utils/LowerExpectIntrinsic.cpp | 23 +++++++++++----
 .../Transforms/LowerExpectIntrinsic/basic.ll  | 29 +++++++++++++++++++
 3 files changed, 51 insertions(+), 5 deletions(-)

diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
index e1880f2bc1e3..52f916e23754 100644
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -8975,8 +8975,12 @@ on the ``min`` argument).
 Syntax:
 """""""
 
+This is an overloaded intrinsic. You can use ``llvm.expect`` on any
+integer bit width.
+
 ::
 
+      declare i1 @llvm.expect.i1(i1 <val>, i1 <expected_val>)
       declare i32 @llvm.expect.i32(i32 <val>, i32 <expected_val>)
       declare i64 @llvm.expect.i64(i64 <val>, i64 <expected_val>)
 
diff --git a/llvm/lib/Transforms/Utils/LowerExpectIntrinsic.cpp b/llvm/lib/Transforms/Utils/LowerExpectIntrinsic.cpp
index e017f501209d..596fd3711515 100644
--- a/llvm/lib/Transforms/Utils/LowerExpectIntrinsic.cpp
+++ b/llvm/lib/Transforms/Utils/LowerExpectIntrinsic.cpp
@@ -94,15 +94,25 @@ bool LowerExpectIntrinsic::HandleIfExpect(BranchInst *BI) {
     return false;
 
   // Handle non-optimized IR code like:
-  //   %expval = call i64 @llvm.expect.i64.i64(i64 %conv1, i64 1)
+  //   %expval = call i64 @llvm.expect.i64(i64 %conv1, i64 1)
   //   %tobool = icmp ne i64 %expval, 0
   //   br i1 %tobool, label %if.then, label %if.end
+  //
+  // Or the following simpler case:
+  //   %expval = call i1 @llvm.expect.i1(i1 %cmp, i1 1)
+  //   br i1 %expval, label %if.then, label %if.end
+
+  CallInst *CI;
 
   ICmpInst *CmpI = dyn_cast<ICmpInst>(BI->getCondition());
-  if (!CmpI || CmpI->getPredicate() != CmpInst::ICMP_NE)
-    return false;
+  if (!CmpI) {
+    CI = dyn_cast<CallInst>(BI->getCondition());
+  } else {
+    if (CmpI->getPredicate() != CmpInst::ICMP_NE)
+      return false;
+    CI = dyn_cast<CallInst>(CmpI->getOperand(0));
+  }
 
-  CallInst *CI = dyn_cast<CallInst>(CmpI->getOperand(0));
   if (!CI)
     return false;
 
@@ -127,7 +137,10 @@ bool LowerExpectIntrinsic::HandleIfExpect(BranchInst *BI) {
 
   BI->setMetadata(LLVMContext::MD_prof, Node);
 
-  CmpI->setOperand(0, ArgValue);
+  if (CmpI)
+    CmpI->setOperand(0, ArgValue);
+  else
+    BI->setCondition(ArgValue);
   return true;
 }
 
diff --git a/llvm/test/Transforms/LowerExpectIntrinsic/basic.ll b/llvm/test/Transforms/LowerExpectIntrinsic/basic.ll
index 955209af14a6..e184cb05b94a 100644
--- a/llvm/test/Transforms/LowerExpectIntrinsic/basic.ll
+++ b/llvm/test/Transforms/LowerExpectIntrinsic/basic.ll
@@ -245,6 +245,35 @@ return:                                           ; preds = %if.end, %if.then
 
 declare i32 @llvm.expect.i32(i32, i32) nounwind readnone
 
+; CHECK-LABEL: @test9(
+define i32 @test9(i32 %x) nounwind uwtable ssp {
+entry:
+  %retval = alloca i32, align 4
+  %x.addr = alloca i32, align 4
+  store i32 %x, i32* %x.addr, align 4
+  %tmp = load i32* %x.addr, align 4
+  %cmp = icmp sgt i32 %tmp, 1
+  %expval = call i1 @llvm.expect.i1(i1 %cmp, i1 1)
+; CHECK: !prof !0
+; CHECK-NOT: @llvm.expect
+  br i1 %expval, label %if.then, label %if.end
+
+if.then:                                          ; preds = %entry
+  %call = call i32 (...)* @f()
+  store i32 %call, i32* %retval
+  br label %return
+
+if.end:                                           ; preds = %entry
+  store i32 1, i32* %retval
+  br label %return
+
+return:                                           ; preds = %if.end, %if.then
+  %0 = load i32* %retval
+  ret i32 %0
+}
+
+declare i1 @llvm.expect.i1(i1, i1) nounwind readnone
+
 ; CHECK: !0 = metadata !{metadata !"branch_weights", i32 64, i32 4}
 ; CHECK: !1 = metadata !{metadata !"branch_weights", i32 4, i32 64}
 ; CHECK: !2 = metadata !{metadata !"branch_weights", i32 4, i32 64, i32 4}