[ValueTracking] fix library to intrinsic mapping to respect 'nobuilti…

…n' attribute

This is another problem raised in:
http://bugs.llvm.org/PR46627

llvm/lib/Analysis/ValueTracking.cpp

@@ -3133,21 +3133,14 @@ Intrinsic::ID llvm::getIntrinsicForCallSite(const CallBase &CB,
   if (F->isIntrinsic())
     return F->getIntrinsicID();
 
-  if (!TLI)
-    return Intrinsic::not_intrinsic;
-
+  // We are going to infer semantics of a library function based on mapping it
+  // to an LLVM intrinsic. Check that the library function is available from
+  // this callbase and in this environment.
   LibFunc Func;
-  // We're going to make assumptions on the semantics of the functions, check
-  // that the target knows that it's available in this environment and it does
-  // not have local linkage.
-  if (!F || F->hasLocalLinkage() || !TLI->getLibFunc(*F, Func))
-    return Intrinsic::not_intrinsic;
-
-  if (!CB.onlyReadsMemory())
+  if (F->hasLocalLinkage() || !TLI || !TLI->getLibFunc(CB, Func) ||
+      !CB.onlyReadsMemory())
     return Intrinsic::not_intrinsic;
 
-  // Otherwise check if we have a call to a function that can be turned into a
-  // vector intrinsic.
   switch (Func) {
   default:
     break;

llvm/test/Transforms/InstSimplify/call.ll

@@ -1039,12 +1039,13 @@ define i32 @call_undef_musttail() {
   ret i32 %x
 }
 
-; FIXME: This is not the builtin fmax, so we don't know anything about its behavior.
+; This is not the builtin fmax, so we don't know anything about its behavior.
 
 define float @nobuiltin_fmax() {
 ; CHECK-LABEL: @nobuiltin_fmax(
 ; CHECK-NEXT:    [[M:%.*]] = call float @fmaxf(float 0.000000e+00, float 1.000000e+00) #3
-; CHECK-NEXT:    ret float [[M]]
+; CHECK-NEXT:    [[R:%.*]] = call float @llvm.fabs.f32(float [[M]])
+; CHECK-NEXT:    ret float [[R]]
 ;
   %m = call float @fmaxf(float 0.0, float 1.0) #0
   %r = call float @llvm.fabs.f32(float %m)