[gfortran,patch] Improve handling of character SELECT

[FX Coudert <fxcoudert at gmail dot com>]

The patch attached is a partial rewrite of the translation of SELECT  
for character types. Currently, we generate a blocks of code for each  
case, along with a label and a list of the cases; a library function  
is called and it returns the address of the label that we will jump  
to. This use of jumps (GOTO_EXPR) is apparently hard on the middle-  
end (probably causing missed-optimizations, and at least preventing  
it to correctly understand what variables are initialized: see PR  
32035). Andrew Pinski suggested that we can use a SWITCH_EXPR instead  
(thanks Andrew for the analysis!). This is what my patch does, by  
assiging an integer value to each case, making the library function  
return an integer value and using a switch to select the appropriate  
code block to execute.

Bootstrapped and regtested on x86_64-linux, OK for mainline?


:ADDPATCH fortran:

Attachment: select_char.ChangeLog
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Attachment: select_char.diff
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