Assertion error in function pointer fmt::Debug implementation - LLVM ERROR: Cannot select: t2: i16 = addrspacecast[1 -> 0] #143
Comments
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Here is the IR of the failing function ; <&T as core::fmt::Debug>::fmt
; Function Attrs: uwtable
define internal zeroext i1 @"_ZN42_$LT$$RF$T$u20$as$u20$core..fmt..Debug$GT$3fmt17hbd9cadb576049f93E"({ i8*, i8* } ({}*) addrspace(1)*** noalias nocapture readonly align 1 dereferenceable(2) %self, %"fmt::Formatter"* align 1 dereferenceable(27) %f) unnamed_addr addrspace(1) #6 {
start:
%buf.i.i.i.i = alloca [128 x i8], align 1
%0 = bitcast { i8*, i8* } ({}*) addrspace(1)*** %self to {} addrspace(1)***
%1 = load {} addrspace(1)**, {} addrspace(1)*** %0, align 1, !nonnull !456
%2 = load {} addrspace(1)*, {} addrspace(1)** %1, align 1, !alias.scope !5154, !nonnull !456
%3 = addrspacecast {} addrspace(1)* %2 to {}*
%4 = ptrtoint {}* %3 to i16
%5 = getelementptr inbounds %"fmt::Formatter", %"fmt::Formatter"* %f, i16 0, i32 7, i32 0
%6 = load i8, i8* %5, align 1, !range !2, !noalias !5157
%7 = getelementptr inbounds %"fmt::Formatter", %"fmt::Formatter"* %f, i16 0, i32 7, i32 1
%8 = load i16, i16* %7, align 1, !noalias !5157
%9 = bitcast %"fmt::Formatter"* %f to i32*
%10 = load i32, i32* %9, align 1, !noalias !5157
%11 = and i32 %10, 4
%12 = icmp eq i32 %11, 0
br i1 %12, label %bb6.i.i, label %bb2.i.i
bb2.i.i: ; preds = %start
%13 = or i32 %10, 8
store i32 %13, i32* %9, align 1, !noalias !5157
%14 = icmp eq i8 %6, 0
br i1 %14, label %bb3.i.i, label %bb6.i.i
bb3.i.i: ; preds = %bb2.i.i
store i16 6, i16* %7, align 1, !noalias !5157
store i8 1, i8* %5, align 1, !noalias !5157
br label %bb6.i.i
bb6.i.i: ; preds = %bb3.i.i, %bb2.i.i, %start
%15 = phi i32 [ %10, %start ], [ %13, %bb3.i.i ], [ %13, %bb2.i.i ]
%16 = or i32 %15, 4
store i32 %16, i32* %9, align 1, !noalias !5157
%17 = getelementptr inbounds [128 x i8], [128 x i8]* %buf.i.i.i.i, i16 0, i16 0
call addrspace(1) void @llvm.lifetime.start.p0i8(i64 128, i8* nonnull %17), !noalias !5160
%18 = getelementptr inbounds [128 x i8], [128 x i8]* %buf.i.i.i.i, i16 0, i16 128
br label %bb15.i.i.i.i
bb15.i.i.i.i: ; preds = %bb15.i.i.i.i, %bb6.i.i
%iter.sroa.4.0.i.i.i.i = phi i8* [ %18, %bb6.i.i ], [ %19, %bb15.i.i.i.i ]
%x.0.i.i.i.i = phi i16 [ %4, %bb6.i.i ], [ %20, %bb15.i.i.i.i ]
%curr.0.i.i.i.i = phi i16 [ 128, %bb6.i.i ], [ %26, %bb15.i.i.i.i ]
%19 = getelementptr inbounds i8, i8* %iter.sroa.4.0.i.i.i.i, i16 -1
%20 = lshr i16 %x.0.i.i.i.i, 4
%21 = trunc i16 %x.0.i.i.i.i to i8
%22 = and i8 %21, 15
%23 = icmp ult i8 %22, 10
%24 = or i8 %22, 48
%25 = add nuw nsw i8 %22, 87
%_0.0.i15.i.i.i.i = select i1 %23, i8 %24, i8 %25
store i8 %_0.0.i15.i.i.i.i, i8* %19, align 1, !noalias !5160
%26 = add nsw i16 %curr.0.i.i.i.i, -1
%27 = icmp eq i16 %20, 0
br i1 %27, label %bb43.i.i.i.i, label %bb15.i.i.i.i
bb43.i.i.i.i: ; preds = %bb15.i.i.i.i
%28 = icmp ugt i16 %26, 128
br i1 %28, label %bb1.i.i.i.i.i.i.i, label %"_ZN4core3ptr87_$LT$impl$u20$core..fmt..Debug$u20$for$u20$unsafe$u20$fn$LP$A$RP$$u20$.$GT$$u20$Ret$GT$3fmt17ha5a3565824dd93e2E.exit"
bb1.i.i.i.i.i.i.i: ; preds = %bb43.i.i.i.i
; call core::slice::slice_index_order_fail
tail call addrspace(1) void @_ZN4core5slice22slice_index_order_fail17h1a521a1329c8fcf9E(i16 %26, i16 128) #17, !noalias !5160
unreachable
"_ZN4core3ptr87_$LT$impl$u20$core..fmt..Debug$u20$for$u20$unsafe$u20$fn$LP$A$RP$$u20$.$GT$$u20$Ret$GT$3fmt17ha5a3565824dd93e2E.exit": ; preds = %bb43.i.i.i.i
%29 = getelementptr inbounds [128 x i8], [128 x i8]* %buf.i.i.i.i, i16 0, i16 %26
%30 = sub i16 129, %curr.0.i.i.i.i
%_3.sroa.0.0._3.sroa.0.0..cast.i.i.i.i.i = bitcast i8* %29 to [0 x i8]*
; call core::fmt::Formatter::pad_integral
%31 = call zeroext addrspace(1) i1 @_ZN4core3fmt9Formatter12pad_integral17h8cbb788acd2ae784E(%"fmt::Formatter"* nonnull align 1 dereferenceable(27) %f, i1 zeroext true, [0 x i8]* noalias nonnull readonly align 1 bitcast (<{ [2 x i8] }>* @anon.1eadd1440c2e72f10a9c27e27f9e4574.191 to [0 x i8]*), i16 2, [0 x i8]* noalias nonnull readonly align 1 %_3.sroa.0.0._3.sroa.0.0..cast.i.i.i.i.i, i16 %30), !noalias !5160
call addrspace(1) void @llvm.lifetime.end.p0i8(i64 128, i8* nonnull %17), !noalias !5160
store i8 %6, i8* %5, align 1, !noalias !5157
store i16 %8, i16* %7, align 1, !noalias !5157
store i32 %10, i32* %9, align 1, !noalias !5157
ret i1 %31
} |
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It seems like LLVM/Rust is choking because when debug printing function pointers. This is the shoddy IR %3 = addrspacecast {} addrspace(1)* %2 to {}*
%4 = ptrtoint {}* %3 to i16In order to convert an Think of it like this On AVR, you cannot convert a PROGMEM function pointer into a RAM pointer (the physical memory spaces are disjoint). Also, it probably makes more sense to print the PROGMEM function pointer when debug printing functions. We should just go I am not sure if it is possible to implement the We need to modify Rust so that it does not attempt this address space conversion and instead use |
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dylanmckay
changed the title
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Have we yet figured out which function pointer is being printed? |
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Not sure, but I've managed to work around it by replacing the implementation of the function pointer As of 20 seconds ago, I successfully compiled the blink program to an ELF under release mode with this branch (current tip 8b7240e). |
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We do have a history of adding hacks like that (especially to the formatting infrastructure) to get things working again. I'd be cool with adding it, changed to hard-code the string |
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Good point, I've updated the commit and pushed 8b7240e. |
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The current patch is this diff --git a/src/libcore/ptr/mod.rs b/src/libcore/ptr/mod.rs
index a04bb11311..caef99ca47 100644
--- a/src/libcore/ptr/mod.rs
+++ b/src/libcore/ptr/mod.rs
@@ -2631,14 +2631,14 @@ macro_rules! fnptr_impls_safety_abi {
#[stable(feature = "fnptr_impls", since = "1.4.0")]
impl<Ret, $($Arg),*> fmt::Pointer for $FnTy {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
- "disabled due to avr-rust/rust#143".fmt(f)
+ fmt::Pointer::fmt(&(*self as usize as *const ()), f)
}
}
#[stable(feature = "fnptr_impls", since = "1.4.0")]
impl<Ret, $($Arg),*> fmt::Debug for $FnTy {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
- "disabled due to avr-rust/rust#143".fmt(f)
+ fmt::Pointer::fmt(&(*self as usize as *const ()), f)
}
}
}Preserving @shepmaster's comment from #137.
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This occurs outside of Debug formatting. For example, the implementations of async/await executors do function pointer conversions. This could be really annoying. |
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Tiny Rust example: fn alpha(i: i32) -> i32 { i + 1 }
static FOO: fn(i32) -> i32 = alpha;The arguments to This fails at if (SrcPtrTy->getAddressSpace() != DstPtrTy->getAddressSpace()) |
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eddyb walked me through something that seems to at least compile; I've hit other issues with async/await so my program as a whole doesn't link, but might be worth someone else trying this patch out and seeing if the weird cast we added for Debug can be avoided with it: commit f7d396073a3adb5ab8ddcd203cd31abeb8ee7d21
Author: Jake Goulding <[email protected]>
Date: Thu Jun 13 15:42:36 2019 -0400
Special-case this function pointer thing
diff --git a/src/librustc_codegen_llvm/common.rs b/src/librustc_codegen_llvm/common.rs
index 0b23aac522..5cab9f47db 100644
--- a/src/librustc_codegen_llvm/common.rs
+++ b/src/librustc_codegen_llvm/common.rs
@@ -308,6 +308,7 @@ impl ConstMethods<'tcx> for CodegenCx<'ll, 'tcx> {
}
},
Scalar::Ptr(ptr) => {
+ let mut do_something_special = false;
let alloc_kind = self.tcx.alloc_map.lock().get(ptr.alloc_id);
let base_addr = match alloc_kind {
Some(GlobalAlloc::Memory(alloc)) => {
@@ -319,6 +320,7 @@ impl ConstMethods<'tcx> for CodegenCx<'ll, 'tcx> {
}
}
Some(GlobalAlloc::Function(fn_instance)) => {
+ do_something_special = true;
self.get_fn(fn_instance)
}
Some(GlobalAlloc::Static(def_id)) => {
@@ -327,15 +329,19 @@ impl ConstMethods<'tcx> for CodegenCx<'ll, 'tcx> {
}
None => bug!("missing allocation {:?}", ptr.alloc_id),
};
- let llval = unsafe { llvm::LLVMConstInBoundsGEP(
- self.const_bitcast(base_addr, self.type_i8p()),
- &self.const_usize(ptr.offset.bytes()),
- 1,
- ) };
- if layout.value != layout::Pointer {
- unsafe { llvm::LLVMConstPtrToInt(llval, llty) }
+ if do_something_special {
+ return base_addr; // move to match?
} else {
- self.const_bitcast(llval, llty)
+ let llval = unsafe { llvm::LLVMConstInBoundsGEP(
+ self.const_bitcast(base_addr, self.type_i8p()),
+ &self.const_usize(ptr.offset.bytes()),
+ 1,
+ ) };
+ if layout.value != layout::Pointer {
+ unsafe { llvm::LLVMConstPtrToInt(llval, llty) }
+ } else {
+ self.const_bitcast(llval, llty)
+ }
}
}
} |
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An updated version of the previous patch diff --git a/src/librustc_codegen_llvm/common.rs b/src/librustc_codegen_llvm/common.rs
index a5cda5949ee..fdbf222549e 100644
--- a/src/librustc_codegen_llvm/common.rs
+++ b/src/librustc_codegen_llvm/common.rs
@@ -244,6 +244,8 @@ impl ConstMethods<'tcx> for CodegenCx<'ll, 'tcx> {
}
}
Scalar::Ptr(ptr) => {
+ let mut do_something_special = false;
+
let base_addr = match self.tcx.global_alloc(ptr.alloc_id) {
GlobalAlloc::Memory(alloc) => {
let init = const_alloc_to_llvm(self, alloc);
@@ -256,24 +258,31 @@ impl ConstMethods<'tcx> for CodegenCx<'ll, 'tcx> {
}
value
}
- GlobalAlloc::Function(fn_instance) => self.get_fn_addr(fn_instance),
+ GlobalAlloc::Function(fn_instance) => {
+ do_something_special = true;
+ self.get_fn_addr(fn_instance)
+ },
GlobalAlloc::Static(def_id) => {
assert!(self.tcx.is_static(def_id));
assert!(!self.tcx.is_thread_local_static(def_id));
self.get_static(def_id)
}
};
- let llval = unsafe {
- llvm::LLVMConstInBoundsGEP(
- self.const_bitcast(base_addr, self.type_i8p()),
- &self.const_usize(ptr.offset.bytes()),
- 1,
- )
- };
- if layout.value != Pointer {
- unsafe { llvm::LLVMConstPtrToInt(llval, llty) }
+ if do_something_special {
+ return base_addr; // move to match?
} else {
- self.const_bitcast(llval, llty)
+ let llval = unsafe {
+ llvm::LLVMConstInBoundsGEP(
+ self.const_bitcast(base_addr, self.type_i8p()),
+ &self.const_usize(ptr.offset.bytes()),
+ 1,
+ )
+ };
+ if layout.value != Pointer {
+ unsafe { llvm::LLVMConstPtrToInt(llval, llty) }
+ } else {
+ self.const_bitcast(llval, llty)
+ }
}
}
}Applying this does seem to prevent some of the newly-added function pointer casts I see, but I have other failures down the line. |
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Thanks for re-pining this @shepmaster, I lost track of this. I've been working on address space cast fixes in the same area here: rust-lang#73270 I will try and merge the patch into the PR. |
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I actually expect that your changes, being more thorough, may have the possibility of making this diff obsolete (fingers crossed) |
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That makes sense - the "other failures down the line" - were they related to function pointer casts? I'm curious because it would be an interesting data point if that patch fixed all/majority of them. I'm still wrestling with rustc (in particular, I believe a |
I believe so, but it was a year ago, so my memory is fuzzy. IIRC, I was trying to get some async executors to work on AVR. Those do make use of function pointers to create a manual vtable. FWIW, if I combine
Then my error when compiling libcore changes: |
Raised from discussion on #137.
The bug is exposed by the
std::fmt::Debugimplementation for functions and function pointers. Rust emits a pointer dereference with a target pointer type ofaddrspace(0)* i16, using LLVM routines that will implicitly insert a bitcast (iN -> iM bits) or an address space cast if necessary. In the case of function pointers, Rust should codegen aaddrspace(1)* i16pointer, so that LLVM doesn't have to map (addrspacecast) PROGMEM pointers to RAM pointers an impossible task because there is no memory mapping and the address spaces do not overlap.Here is the full LLVM IR for
libcorefrom the #137 branch libcore.ll.The text was updated successfully, but these errors were encountered: