[PATCH] D101036: [WebAssembly] Fix fixEndsAtEndOfFunction for delegate

[Heejin Ahn via Phabricator via llvm-commits]

aheejin created this revision.
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Background:
CFGStackify's `fixEndsAtEndOfFunction` fixes block/loop/try's return
type when the end of function is unreachable and the function return
type is not void. So if a function returns i32 and `block`-`end` wraps the
whole function, i.e., the `block`'s `end` is the last instruction of the
function, the `block`'s return type should be i32 too:

  block i32
    ...
  end
  end_function

If there are consecutive `end`s, this signature has to be propagate to
those blocks too, like:

  block i32
    ...
    block i32
      ...
    end
  end
  end_function

This applies to `try`-`end` too:

  try i32
    ...
  catch
    ...
  end
  end_function

In case of `try`, we not only follow consecutive `end`s but also follow
`catch`, because for the type of the whole `try` to be i32, both `try`
and `catch` parts have to be i32:

  try i32
    ...
    block i32
      ...
    end
  catch
    ...
    block i32
      ...
    end
  end
  end_function



---

Previously we only handled consecutive `end`s or `end` before a `catch`.
But now we have `delegate`, which serves like `end` for
`try`-`delegate`. So we have to follow `delegate` too and mark its
corresponding `try` as i32 (the function's return type):

  try i32
    ...
  catch
    ...
    try i32    ;; Here
      ...
    delegate N
  end
  end_function


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D101036

Files:
  llvm/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp
  llvm/test/CodeGen/WebAssembly/cfg-stackify-eh.mir


Index: llvm/test/CodeGen/WebAssembly/cfg-stackify-eh.mir
===================================================================
--- llvm/test/CodeGen/WebAssembly/cfg-stackify-eh.mir
+++ llvm/test/CodeGen/WebAssembly/cfg-stackify-eh.mir
@@ -9,6 +9,9 @@
   define void @rethrow_arg_test() personality i8* bitcast (i32 (...)* @__gxx_wasm_personality_v0 to i8*) {
     ret void
   }
+  define i32 @fix_end_function_test() personality i8* bitcast (i32 (...)* @__gxx_wasm_personality_v0 to i8*) {
+    ret i32 0
+  }
 ...
 
 ---
@@ -43,7 +46,7 @@
     ; CHECK: bb.2 (landing-pad):
     ; CHECK: CATCH
     ; CHECK: RETHROW 0
-    EH_LABEL <mcsymbol .Ltmp5>
+    EH_LABEL <mcsymbol .Ltmp3>
     %1:i32 = CATCH &__cpp_exception, implicit-def dead $arguments
     RETHROW 0, implicit-def dead $arguments
 
@@ -53,3 +56,61 @@
     ; CHECK: END_TRY
     RETURN implicit-def dead $arguments
 ...
+
+---
+# This function has i32 return type and the end of the function is unreachable,
+# so CFGStackify's fixEndsAtEndOfFunction() propagates the return type while
+# they encounter 'end' or 'delegate'. This is a regression test for a bug that
+# we only handled 'end' but not 'delegate'.
+# CHECK-LABEL: name: fix_end_function_test
+name: fix_end_function_test
+liveins:
+  - { reg: '$arguments' }
+machineFunctionInfo:
+  params:          [  ]
+  results:         [ i32 ]
+  wasmEHFuncInfo:
+    3:               4
+body: |
+  ; CHECK: TRY 127
+  ; CHECK:   TRY 127
+  ; CHECK:     CALL @foo
+  ; CHECK:     TRY 64
+  ; CHECK:       CALL @foo
+  ; CHECK:     DELEGATE
+  ; CHECK:     RETURN
+  ; CHECK:   CATCH
+  ;; This TRY should have the return type i32 (127)
+  ; CHECK:     TRY 127
+  ; CHECK:       RETHROW
+  ; CHECK:     DELEGATE
+  ; CHECK:   END_TRY
+  ; CHECK: CATCH
+  ; CHECK:   RETHROW
+  ; CHECK: END_TRY
+  bb.0:
+    successors: %bb.1, %bb.3
+    EH_LABEL <mcsymbol .Ltmp0>
+    CALL @foo, implicit-def dead $arguments, implicit $sp32, implicit $sp64
+    EH_LABEL <mcsymbol .Ltmp1>
+
+  bb.1:
+    successors: %bb.2, %bb.4
+    EH_LABEL <mcsymbol .Ltmp2>
+    CALL @foo, implicit-def dead $arguments, implicit $sp32, implicit $sp64
+    EH_LABEL <mcsymbol .Ltmp3>
+
+  bb.2:
+    %0:i32 = CONST_I32 3, implicit-def dead $arguments
+    RETURN %0:i32, implicit-def dead $arguments
+
+  bb.3 (landing-pad):
+    EH_LABEL <mcsymbol .Ltmp4>
+    %0:i32 = CATCH &__cpp_exception, implicit-def dead $arguments
+    RETHROW 0, implicit-def dead $arguments
+
+  bb.4 (landing-pad):
+    EH_LABEL <mcsymbol .Ltmp5>
+    %1:i32 = CATCH &__cpp_exception, implicit-def dead $arguments
+    RETHROW 0, implicit-def dead $arguments
+...
Index: llvm/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp
===================================================================
--- llvm/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp
+++ llvm/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp
@@ -1524,6 +1524,7 @@
       }
       case WebAssembly::END_BLOCK:
       case WebAssembly::END_LOOP:
+      case WebAssembly::DELEGATE:
         EndToBegin[&MI]->getOperand(0).setImm(int32_t(RetType));
         continue;
       default:


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