TargetLibraryInfo: Stop guessing wchar_t size

Usually the frontend communicates the size of wchar_t via metadata and
we can optimize wcslen (and possibly other calls in the future). In
cases without the wchar_size metadata we would previously try to guess
the correct size based on the target triple; however this is fragile to
keep up to date and may miss users manually changing the size via flags.
Better be safe and stop guessing and optimizing if the frontend didn't
communicate the size.

Differential Revision: https://reviews.llvm.org/D38106

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@314185 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/Analysis/TargetLibraryInfo.h b/include/llvm/Analysis/TargetLibraryInfo.h
index d75e783..a3fe834 100644 (file)
--- a/include/llvm/Analysis/TargetLibraryInfo.h
+++ b/include/llvm/Analysis/TargetLibraryInfo.h
@@ -193,13 +193,9 @@ public:
     ShouldSignExtI32Param = Val;
   }
 
-  /// Returns the size of the wchar_t type in bytes.
+  /// Returns the size of the wchar_t type in bytes or 0 if the size is unknown.
+  /// This queries the 'wchar_size' metadata.
   unsigned getWCharSize(const Module &M) const;
-
-  /// Returns size of the default wchar_t type on target \p T. This is mostly
-  /// intended to verify that the size in the frontend matches LLVM. All other
-  /// queries should use getWCharSize() instead.
-  static unsigned getTargetWCharSize(const Triple &T);
 };
 
 /// Provides information about what library functions are available for

diff --git a/lib/Analysis/TargetLibraryInfo.cpp b/lib/Analysis/TargetLibraryInfo.cpp
index 2be5d5c..47a84bd 100644 (file)
--- a/lib/Analysis/TargetLibraryInfo.cpp
+++ b/lib/Analysis/TargetLibraryInfo.cpp
@@ -1519,20 +1519,11 @@ TargetLibraryInfoImpl &TargetLibraryAnalysis::lookupInfoImpl(const Triple &T) {
   return *Impl;
 }
 
-unsigned TargetLibraryInfoImpl::getTargetWCharSize(const Triple &T) {
-  // See also clang/lib/Basic/Targets.cpp.
-  if (T.isPS4() || T.isOSWindows() || T.isArch16Bit())
-    return 2;
-  if (T.getArch() == Triple::xcore)
-    return 1;
-  return 4;
-}
-
 unsigned TargetLibraryInfoImpl::getWCharSize(const Module &M) const {
   if (auto *ShortWChar = cast_or_null<ConstantAsMetadata>(
       M.getModuleFlag("wchar_size")))
     return cast<ConstantInt>(ShortWChar->getValue())->getZExtValue();
-  return getTargetWCharSize(Triple(M.getTargetTriple()));
+  return 0;
 }
 
 TargetLibraryInfoWrapperPass::TargetLibraryInfoWrapperPass()

diff --git a/lib/Transforms/Utils/SimplifyLibCalls.cpp b/lib/Transforms/Utils/SimplifyLibCalls.cpp
index 37cfc2c..22c078a 100644 (file)
--- a/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ b/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -508,6 +508,9 @@ Value *LibCallSimplifier::optimizeStrLen(CallInst *CI, IRBuilder<> &B) {
 Value *LibCallSimplifier::optimizeWcslen(CallInst *CI, IRBuilder<> &B) {
   Module &M = *CI->getParent()->getParent()->getParent();
   unsigned WCharSize = TLI->getWCharSize(M) * 8;
+  // We cannot perform this optimization without wchar_size metadata.
+  if (WCharSize == 0)
+    return nullptr;
 
   return optimizeStringLength(CI, B, WCharSize);
 }

diff --git a/test/Transforms/InstCombine/wcslen-1.ll b/test/Transforms/InstCombine/wcslen-1.ll
index cdde1bf..22da95e 100644 (file)
--- a/test/Transforms/InstCombine/wcslen-1.ll
+++ b/test/Transforms/InstCombine/wcslen-1.ll
@@ -7,6 +7,9 @@ target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
 
 declare i64 @wcslen(i32*)
 
+!0 = !{i32 1, !"wchar_size", i32 4}
+!llvm.module.flags = !{!0}
+
 @hello = constant [6 x i32] [i32 104, i32 101, i32 108, i32 108, i32 111, i32 0]
 @longer = constant [7 x i32] [i32 108, i32 111, i32 110, i32 103, i32 101, i32 114, i32 0]
 @null = constant [1 x i32] zeroinitializer

diff --git a/test/Transforms/InstCombine/wcslen-2.ll b/test/Transforms/InstCombine/wcslen-2.ll
index c1a7031..15f1fdb 100644 (file)
--- a/test/Transforms/InstCombine/wcslen-2.ll
+++ b/test/Transforms/InstCombine/wcslen-2.ll
@@ -4,6 +4,9 @@
 
 target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
 
+!0 = !{i32 1, !"wchar_size", i32 4}
+!llvm.module.flags = !{!0}
+
 @hello = constant [6 x i32] [i32 104, i32 101, i32 108, i32 108, i32 111, i32 0]
 
 declare i64 @wcslen(i32*, i32)

diff --git a/test/Transforms/InstCombine/wcslen-4.ll b/test/Transforms/InstCombine/wcslen-4.ll
new file mode 100644 (file)
index 0000000..0783228
--- /dev/null
+++ b/test/Transforms/InstCombine/wcslen-4.ll
@@ -0,0 +1,20 @@
+; Test that the wcslen library call simplifier works correctly.
+;
+; RUN: opt < %s -instcombine -S | FileCheck %s
+
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+
+; Without the wchar_size metadata we should see no optimization happening.
+
+@hello = constant [6 x i32] [i32 104, i32 101, i32 108, i32 108, i32 111, i32 0]
+
+declare i64 @wcslen(i32*)
+
+define i64 @test_no_simplify1() {
+; CHECK-LABEL: @test_no_simplify1(
+; CHECK-NEXT: %hello_l = call i64 @wcslen(i32* getelementptr inbounds ([6 x i32], [6 x i32]* @hello, i64 0, i64 0))
+; CHECK-NEXT: ret i64 %hello_l
+  %hello_p = getelementptr [6 x i32], [6 x i32]* @hello, i64 0, i64 0
+  %hello_l = call i64 @wcslen(i32* %hello_p)
+  ret i64 %hello_l
+}