[patch] mergefunc struct result

[Carlo Kok]

When using the merge func pass with two functions that return the same
kind of struct but with different element types merge func tries to do a
bitcast of struct to struct and fails with an assert (as you can't bitcast  
a struct) given the following functions:

%kv1 = type { i32*, i32* }
%kv2 = type { i8*, i8* }

define %kv1 @fn1() ..
define %kv2 @fn2() ..

(full file in fail.ir)

The attached patch checks for two struct types & uses insert/extract to
create the right record.

To see it fail, fail.ir can be used with opt:

opt -mergefunc fail.ir -o out.ir

after the patch it generates:

define %kv1 @fn1() {
   %tmp = alloca %kv1
   %v1 = getelementptr %kv1* %tmp, i32 0, i32 0
   store i32* null, i32** %v1
   %v2 = getelementptr %kv1* %tmp, i32 0, i32 0
   store i32* null, i32** %v2
   call void @noop()
   %v3 = load %kv1* %tmp
   ret %kv1 %v3
}

define %kv2 @fn2() {
   %1 = tail call %kv1 @fn1()
   %2 = extractvalue %kv1 %1, 0
   %3 = bitcast i32* %2 to i8*
   %4 = insertvalue %kv2 undef, i8* %3, 0
   %5 = extractvalue %kv1 %1, 1
   %6 = bitcast i32* %5 to i8*
   %7 = insertvalue %kv2 %4, i8* %6, 1
   ret %kv2 %7
}

Where fn2 is the merged function.

-- 
Carlo Kok
RemObjects Software
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