instcombine: Migrate strlen optimizations

This patch migrates the strlen optimizations from the simplify-libcalls
pass into the instcombine library call simplifier.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167103 91177308-0d34-0410-b5e6-96231b3b80d8

5 files changed, 160 insertions, 106 deletions

diff --git a/lib/Transforms/Scalar/SimplifyLibCalls.cpp b/lib/Transforms/Scalar/SimplifyLibCalls.cpp
index 4251e60a91..a0235c15b6 100644
--- a/lib/Transforms/Scalar/SimplifyLibCalls.cpp
+++ b/lib/Transforms/Scalar/SimplifyLibCalls.cpp
@@ -90,22 +90,6 @@ public:
 // Helper Functions
 //===----------------------------------------------------------------------===//
 
-/// IsOnlyUsedInZeroEqualityComparison - Return true if it only matters that the
-/// value is equal or not-equal to zero.
-static bool IsOnlyUsedInZeroEqualityComparison(Value *V) {
-  for (Value::use_iterator UI = V->use_begin(), E = V->use_end();
-       UI != E; ++UI) {
-    if (ICmpInst *IC = dyn_cast<ICmpInst>(*UI))
-      if (IC->isEquality())
-        if (Constant *C = dyn_cast<Constant>(IC->getOperand(1)))
-          if (C->isNullValue())
-            continue;
-    // Unknown instruction.
-    return false;
-  }
-  return true;
-}
-
 static bool CallHasFloatingPointArgument(const CallInst *CI) {
   for (CallInst::const_op_iterator it = CI->op_begin(), e = CI->op_end();
        it != e; ++it) {
@@ -135,32 +119,6 @@ static bool IsOnlyUsedInEqualityComparison(Value *V, Value *With) {
 
 namespace {
 //===---------------------------------------===//
-// 'strlen' Optimizations
-
-struct StrLenOpt : public LibCallOptimization {
-  virtual Value *CallOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
-    FunctionType *FT = Callee->getFunctionType();
-    if (FT->getNumParams() != 1 ||
-        FT->getParamType(0) != B.getInt8PtrTy() ||
-        !FT->getReturnType()->isIntegerTy())
-      return 0;
-
-    Value *Src = CI->getArgOperand(0);
-
-    // Constant folding: strlen("xyz") -> 3
-    if (uint64_t Len = GetStringLength(Src))
-      return ConstantInt::get(CI->getType(), Len-1);
-
-    // strlen(x) != 0 --> *x != 0
-    // strlen(x) == 0 --> *x == 0
-    if (IsOnlyUsedInZeroEqualityComparison(CI))
-      return B.CreateZExt(B.CreateLoad(Src, "strlenfirst"), CI->getType());
-    return 0;
-  }
-};
-
-
-//===---------------------------------------===//
 // 'strpbrk' Optimizations
 
 struct StrPBrkOpt : public LibCallOptimization {
@@ -1146,7 +1104,7 @@ namespace {
 
     StringMap<LibCallOptimization*> Optimizations;
     // String and Memory LibCall Optimizations
-    StrLenOpt StrLen; StrPBrkOpt StrPBrk;
+    StrPBrkOpt StrPBrk;
     StrToOpt StrTo; StrSpnOpt StrSpn; StrCSpnOpt StrCSpn; StrStrOpt StrStr;
     MemCmpOpt MemCmp; MemCpyOpt MemCpy; MemMoveOpt MemMove; MemSetOpt MemSet;
     // Math Library Optimizations
@@ -1215,7 +1173,6 @@ void SimplifyLibCalls::AddOpt(LibFunc::Func F1, LibFunc::Func F2,
 /// we know.
 void SimplifyLibCalls::InitOptimizations() {
   // String and Memory LibCall Optimizations
-  Optimizations["strlen"] = &StrLen;
   Optimizations["strpbrk"] = &StrPBrk;
   Optimizations["strtol"] = &StrTo;
   Optimizations["strtod"] = &StrTo;
diff --git a/lib/Transforms/Utils/SimplifyLibCalls.cpp b/lib/Transforms/Utils/SimplifyLibCalls.cpp
index cc03573326..658e7c3428 100644
--- a/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ b/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -64,6 +64,26 @@ public:
 };
 
 //===----------------------------------------------------------------------===//
+// Helper Functions
+//===----------------------------------------------------------------------===//
+
+/// isOnlyUsedInZeroEqualityComparison - Return true if it only matters that the
+/// value is equal or not-equal to zero.
+static bool isOnlyUsedInZeroEqualityComparison(Value *V) {
+  for (Value::use_iterator UI = V->use_begin(), E = V->use_end();
+       UI != E; ++UI) {
+    if (ICmpInst *IC = dyn_cast<ICmpInst>(*UI))
+      if (IC->isEquality())
+        if (Constant *C = dyn_cast<Constant>(IC->getOperand(1)))
+          if (C->isNullValue())
+            continue;
+    // Unknown instruction.
+    return false;
+  }
+  return true;
+}
+
+//===----------------------------------------------------------------------===//
 // Fortified Library Call Optimizations
 //===----------------------------------------------------------------------===//
 
@@ -675,6 +695,28 @@ struct StrNCpyOpt : public LibCallOptimization {
   }
 };
 
+struct StrLenOpt : public LibCallOptimization {
+  virtual Value *callOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
+    FunctionType *FT = Callee->getFunctionType();
+    if (FT->getNumParams() != 1 ||
+        FT->getParamType(0) != B.getInt8PtrTy() ||
+        !FT->getReturnType()->isIntegerTy())
+      return 0;
+
+    Value *Src = CI->getArgOperand(0);
+
+    // Constant folding: strlen("xyz") -> 3
+    if (uint64_t Len = GetStringLength(Src))
+      return ConstantInt::get(CI->getType(), Len-1);
+
+    // strlen(x) != 0 --> *x != 0
+    // strlen(x) == 0 --> *x == 0
+    if (isOnlyUsedInZeroEqualityComparison(CI))
+      return B.CreateZExt(B.CreateLoad(Src, "strlenfirst"), CI->getType());
+    return 0;
+  }
+};
+
 } // End anonymous namespace.
 
 namespace llvm {
@@ -702,6 +744,7 @@ class LibCallSimplifierImpl {
   StrCpyOpt StrCpy;
   StpCpyOpt StpCpy;
   StrNCpyOpt StrNCpy;
+  StrLenOpt StrLen;
 
   void initOptimizations();
 public:
@@ -733,6 +776,7 @@ void LibCallSimplifierImpl::initOptimizations() {
   Optimizations["strcpy"] = &StrCpy;
   Optimizations["stpcpy"] = &StpCpy;
   Optimizations["strncpy"] = &StrNCpy;
+  Optimizations["strlen"] = &StrLen;
 }
 
 Value *LibCallSimplifierImpl::optimizeCall(CallInst *CI) {
diff --git a/test/Transforms/InstCombine/strlen-1.ll b/test/Transforms/InstCombine/strlen-1.ll
new file mode 100644
index 0000000000..6d7464a4cc
--- /dev/null
+++ b/test/Transforms/InstCombine/strlen-1.ll
@@ -0,0 +1,97 @@
+; Test that the strlen library call simplifier works correctly.
+;
+; RUN: opt < %s -instcombine -S | FileCheck %s
+
+target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
+
+@hello = constant [6 x i8] c"hello\00"
+@null = constant [1 x i8] zeroinitializer
+@null_hello = constant [7 x i8] c"\00hello\00"
+@nullstring = constant i8 0
+@a = common global [32 x i8] zeroinitializer, align 1
+
+declare i32 @strlen(i8*)
+
+; Check strlen(string constant) -> integer constant.
+
+define i32 @test_simplify1() {
+; CHECK: @test_simplify1
+  %hello_p = getelementptr [6 x i8]* @hello, i32 0, i32 0
+  %hello_l = call i32 @strlen(i8* %hello_p)
+  ret i32 %hello_l
+; CHECK-NEXT: ret i32 5
+}
+
+define i32 @test_simplify2() {
+; CHECK: @test_simplify2
+  %null_p = getelementptr [1 x i8]* @null, i32 0, i32 0
+  %null_l = call i32 @strlen(i8* %null_p)
+  ret i32 %null_l
+; CHECK-NEXT: ret i32 0
+}
+
+define i32 @test_simplify3() {
+; CHECK: @test_simplify3
+  %null_hello_p = getelementptr [7 x i8]* @null_hello, i32 0, i32 0
+  %null_hello_l = call i32 @strlen(i8* %null_hello_p)
+  ret i32 %null_hello_l
+; CHECK-NEXT: ret i32 0
+}
+
+define i32 @test_simplify4() {
+; CHECK: @test_simplify4
+  %len = tail call i32 @strlen(i8* @nullstring) nounwind
+  ret i32 %len
+; CHECK-NEXT: ret i32 0
+}
+
+; Check strlen(x) == 0 --> *x == 0.
+
+define i1 @test_simplify5() {
+; CHECK: @test_simplify5
+  %hello_p = getelementptr [6 x i8]* @hello, i32 0, i32 0
+  %hello_l = call i32 @strlen(i8* %hello_p)
+  %eq_hello = icmp eq i32 %hello_l, 0
+  ret i1 %eq_hello
+; CHECK-NEXT: ret i1 false
+}
+
+define i1 @test_simplify6() {
+; CHECK: @test_simplify6
+  %null_p = getelementptr [1 x i8]* @null, i32 0, i32 0
+  %null_l = call i32 @strlen(i8* %null_p)
+  %eq_null = icmp eq i32 %null_l, 0
+  ret i1 %eq_null
+; CHECK-NEXT: ret i1 true
+}
+
+; Check strlen(x) != 0 --> *x != 0.
+
+define i1 @test_simplify7() {
+; CHECK: @test_simplify7
+  %hello_p = getelementptr [6 x i8]* @hello, i32 0, i32 0
+  %hello_l = call i32 @strlen(i8* %hello_p)
+  %ne_hello = icmp ne i32 %hello_l, 0
+  ret i1 %ne_hello
+; CHECK-NEXT: ret i1 true
+}
+
+define i1 @test_simplify8() {
+; CHECK: @test_simplify8
+  %null_p = getelementptr [1 x i8]* @null, i32 0, i32 0
+  %null_l = call i32 @strlen(i8* %null_p)
+  %ne_null = icmp ne i32 %null_l, 0
+  ret i1 %ne_null
+; CHECK-NEXT: ret i1 false
+}
+
+; Check cases that shouldn't be simplified.
+
+define i32 @test_no_simplify1() {
+; CHECK: @test_no_simplify1
+  %a_p = getelementptr [32 x i8]* @a, i32 0, i32 0
+  %a_l = call i32 @strlen(i8* %a_p)
+; CHECK-NEXT: %a_l = call i32 @strlen
+  ret i32 %a_l
+; CHECK-NEXT: ret i32 %a_l
+}
diff --git a/test/Transforms/InstCombine/strlen-2.ll b/test/Transforms/InstCombine/strlen-2.ll
new file mode 100644
index 0000000000..c4fd54c06d
--- /dev/null
+++ b/test/Transforms/InstCombine/strlen-2.ll
@@ -0,0 +1,18 @@
+; Test that the strlen library call simplifier works correctly.
+;
+; RUN: opt < %s -instcombine -S | FileCheck %s
+
+target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
+
+@hello = constant [6 x i8] c"hello\00"
+
+declare i32 @strlen(i8*, i32)
+
+define i32 @test_no_simplify1() {
+; CHECK: @test_no_simplify1
+  %hello_p = getelementptr [6 x i8]* @hello, i32 0, i32 0
+  %hello_l = call i32 @strlen(i8* %hello_p, i32 187)
+; CHECK-NEXT: %hello_l = call i32 @strlen
+  ret i32 %hello_l
+; CHECK-NEXT: ret i32 %hello_l
+}
diff --git a/test/Transforms/SimplifyLibCalls/StrLen.ll b/test/Transforms/SimplifyLibCalls/StrLen.ll
deleted file mode 100644
index 4a20bbd2ce..0000000000
--- a/test/Transforms/SimplifyLibCalls/StrLen.ll
+++ /dev/null
@@ -1,62 +0,0 @@
-; Test that the StrCatOptimizer works correctly
-; RUN: opt < %s -simplify-libcalls -S | \
-; RUN:    not grep "call.*strlen"
-
-target datalayout = "e-p:32:32"
-@hello = constant [6 x i8] c"hello\00"		; <[6 x i8]*> [#uses=3]
-@null = constant [1 x i8] zeroinitializer		; <[1 x i8]*> [#uses=3]
-@null_hello = constant [7 x i8] c"\00hello\00"		; <[7 x i8]*> [#uses=1]
-@nullstring = constant i8 0
-
-declare i32 @strlen(i8*)
-
-define i32 @test1() {
-	%hello_p = getelementptr [6 x i8]* @hello, i32 0, i32 0		; <i8*> [#uses=1]
-	%hello_l = call i32 @strlen( i8* %hello_p )		; <i32> [#uses=1]
-	ret i32 %hello_l
-}
-
-define i32 @test2() {
-	%null_p = getelementptr [1 x i8]* @null, i32 0, i32 0		; <i8*> [#uses=1]
-	%null_l = call i32 @strlen( i8* %null_p )		; <i32> [#uses=1]
-	ret i32 %null_l
-}
-
-define i32 @test3() {
-	%null_hello_p = getelementptr [7 x i8]* @null_hello, i32 0, i32 0		; <i8*> [#uses=1]
-	%null_hello_l = call i32 @strlen( i8* %null_hello_p )		; <i32> [#uses=1]
-	ret i32 %null_hello_l
-}
-
-define i1 @test4() {
-	%hello_p = getelementptr [6 x i8]* @hello, i32 0, i32 0		; <i8*> [#uses=1]
-	%hello_l = call i32 @strlen( i8* %hello_p )		; <i32> [#uses=1]
-	%eq_hello = icmp eq i32 %hello_l, 0		; <i1> [#uses=1]
-	ret i1 %eq_hello
-}
-
-define i1 @test5() {
-	%null_p = getelementptr [1 x i8]* @null, i32 0, i32 0		; <i8*> [#uses=1]
-	%null_l = call i32 @strlen( i8* %null_p )		; <i32> [#uses=1]
-	%eq_null = icmp eq i32 %null_l, 0		; <i1> [#uses=1]
-	ret i1 %eq_null
-}
-
-define i1 @test6() {
-	%hello_p = getelementptr [6 x i8]* @hello, i32 0, i32 0		; <i8*> [#uses=1]
-	%hello_l = call i32 @strlen( i8* %hello_p )		; <i32> [#uses=1]
-	%ne_hello = icmp ne i32 %hello_l, 0		; <i1> [#uses=1]
-	ret i1 %ne_hello
-}
-
-define i1 @test7() {
-	%null_p = getelementptr [1 x i8]* @null, i32 0, i32 0		; <i8*> [#uses=1]
-	%null_l = call i32 @strlen( i8* %null_p )		; <i32> [#uses=1]
-	%ne_null = icmp ne i32 %null_l, 0		; <i1> [#uses=1]
-	ret i1 %ne_null
-}
-
-define i32 @test8() {
-	%len = tail call i32 @strlen(i8* @nullstring) nounwind
-	ret i32 %len
-}