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089fc0dcee
Summary:
When the WebAssembly backend encounters a return type that doesn't
fit within i32, SelectionDAG performs sret demotion, adding an
additional argument to the start of the function that contains
a pointer to an sret buffer to use instead. However, this conflicts
with the emscripten sjlj lowering pass. There we translate calls like:
```
call {i32, i32} @foo()
```
into (in pseudo-llvm)
```
%addr = @foo
call {i32, i32} @__invoke_{i32,i32}(%addr)
```
i.e. we perform an indirect call through an extra function.
However, the sret transform now transforms this into
the equivalent of
```
%addr = @foo
%sret = alloca {i32, i32}
call {i32, i32} @__invoke_{i32,i32}(%sret, %addr)
```
(while simultaneously translation the implementation of @foo as well).
Unfortunately, this doesn't work out. The __invoke_ ABI expected
the function address to be the first argument, causing crashes.
There is several possible ways to fix this:
1. Implementing the sret rewrite at the IR level as well and performing
it as part of lowering to __invoke
2. Fixing the wasm backend to recognize that __invoke has a special ABI
3. A change to the binaryen/emscripten ABI to recognize this situation
This revision implements the middle option, teaching the backend to
treat __invoke_ functions specially in sret lowering. This is achieved
by
1) Introducing a new CallingConv ID for invoke functions
2) When this CallingConv ID is seen in the backend and the first argument
is marked as sret (a function pointer would never be marked as sret),
swapping the first two arguments.
Reviewed By: tlively, aheejin
Differential Revision: https://reviews.llvm.org/D65463
llvm-svn: 367935
66 lines
2.0 KiB
LLVM
66 lines
2.0 KiB
LLVM
; RUN: opt < %s -wasm-lower-em-ehsjlj -emscripten-cxx-exceptions-whitelist=do_catch -S | FileCheck %s
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target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
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target triple = "wasm32-unknown-unknown"
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define void @dont_catch() personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*) {
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; CHECK-LABEL: @dont_catch(
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entry:
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invoke void @foo()
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to label %invoke.cont unwind label %lpad
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; CHECK: entry:
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; CHECK-NEXT: call void @foo()
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; CHECK-NEXT: br label %invoke.cont
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invoke.cont: ; preds = %entry
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br label %try.cont
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lpad: ; preds = %entry
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%0 = landingpad { i8*, i32 }
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catch i8* null
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%1 = extractvalue { i8*, i32 } %0, 0
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%2 = extractvalue { i8*, i32 } %0, 1
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br label %catch
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catch: ; preds = %lpad
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%3 = call i8* @__cxa_begin_catch(i8* %1)
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call void @__cxa_end_catch()
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br label %try.cont
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try.cont: ; preds = %catch, %invoke.cont
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ret void
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}
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define void @do_catch() personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*) {
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; CHECK-LABEL: @do_catch(
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entry:
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invoke void @foo()
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to label %invoke.cont unwind label %lpad
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; CHECK: entry:
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; CHECK-NEXT: store i32 0, i32*
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; CHECK-NEXT: call cc{{.*}} void @__invoke_void(void ()* @foo)
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invoke.cont: ; preds = %entry
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br label %try.cont
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lpad: ; preds = %entry
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%0 = landingpad { i8*, i32 }
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catch i8* null
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%1 = extractvalue { i8*, i32 } %0, 0
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%2 = extractvalue { i8*, i32 } %0, 1
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br label %catch
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catch: ; preds = %lpad
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%3 = call i8* @__cxa_begin_catch(i8* %1)
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call void @__cxa_end_catch()
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br label %try.cont
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try.cont: ; preds = %catch, %invoke.cont
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ret void
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}
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declare void @foo()
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declare i32 @__gxx_personality_v0(...)
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declare i8* @__cxa_begin_catch(i8*)
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declare void @__cxa_end_catch()
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