Don't mark math fns as nounwind, just willreturn (#2807)

* Don't mark math fns as nounwind, just willreturn

* fix

* Update Project.toml

Author: wsmoses

Project.toml

@@ -42,7 +42,7 @@ BFloat16s = "0.2, 0.3, 0.4, 0.5, 0.6"
 CEnum = "0.4, 0.5"
 ChainRulesCore = "1"
 EnzymeCore = "0.8.16"
-Enzyme_jll = "0.0.220"
+Enzyme_jll = "0.0.221"
 GPUArraysCore = "0.1.6, 0.2"
 GPUCompiler = "1.6.2"
 LLVM = "9.1"

src/compiler.jl

@@ -1057,14 +1057,12 @@ end
         LLVM.Attribute[LLVM.EnumAttribute("readnone"), StringAttribute("enzyme_shouldrecompute"),
                     EnumAttribute("willreturn"),
                     EnumAttribute("nosync"),
-                    EnumAttribute("nounwind"),
                     EnumAttribute("nofree"),
 		      ]
     else
         LLVM.Attribute[EnumAttribute("memory", NoEffects.data), StringAttribute("enzyme_shouldrecompute"),
                     EnumAttribute("willreturn"),
                     EnumAttribute("nosync"),
-                    EnumAttribute("nounwind"),
 		    EnumAttribute("nofree")]
     end
     handleCustom(state, custom, k_name, llvmfn, name, attrs)

src/compiler/utils.jl

@@ -146,6 +146,15 @@ Base.@assume_effects :removable :foldable :nothrow function is_noreturn(f::LLVM.
     return false
 end
 
+Base.@assume_effects :removable :foldable :nothrow function is_nounwind(f::LLVM.Function)::Bool
+    for attr in collect(function_attributes(f))
+        if kind(attr) == kind(EnumAttribute("nounwind"))
+            return true
+        end
+    end
+    return false
+end
+
 Base.@assume_effects :removable :foldable :nothrow function is_readonly(f::LLVM.Function)::Bool
     intr = LLVM.API.LLVMGetIntrinsicID(f)
     if intr == LLVM.Intrinsic("llvm.lifetime.start").id

src/llvm/transforms.jl

@@ -1632,7 +1632,7 @@ function remove_readonly_unused_calls!(fn::LLVM.Function, next::Set{String})
             return false
         end
 
-        err_is_readonly = !is_noreturn(cur)
+        err_is_readonly = true
 
         for bb in blocks(cur)
             for inst in instructions(bb)
@@ -1654,7 +1654,7 @@ function remove_readonly_unused_calls!(fn::LLVM.Function, next::Set{String})
 
     changed = set_readonly!(fn)
 
-    if length(calls) == 0 || hasUser
+    if length(calls) == 0 || hasUser || !is_nounwind(fn)
         return changed
     end