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transform: fix bug in StringToBytes optimization pass

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Previously, this pass would convert any read-only use of a
runtime.stringToBytes call to use the original string buffer instead.
This is incorrect: if there are any writes to the resulting buffer, none
of the slice buffer pointers can be converted to use the original
read-only string buffer.

This commit fixes that bug and adds a test to prove the new (correct)
behavior.
This commit is contained in:
Ayke van Laethem
2023-09-21 15:39:06 +02:00
committed by Ron Evans
parent 081d2e58c6
commit a896f7f218
3 changed files with 44 additions and 6 deletions
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transform/testdata/stringtobytes.ll
Vendored
+16
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@@ -30,3 +30,19 @@ entry:
call fastcc void @writeToSlice(ptr %1, i64 %2, i64 %3)
ret void
}
; Test that pointer values are never propagated if there is even a single write
; to the pointer value (but len/cap values still can be).
define void @testReadSome() {
entry:
%s = call fastcc { ptr, i64, i64 } @runtime.stringToBytes(ptr @str, i64 6)
%s.ptr = extractvalue { ptr, i64, i64 } %s, 0
%s.len = extractvalue { ptr, i64, i64 } %s, 1
%s.cap = extractvalue { ptr, i64, i64 } %s, 2
call fastcc void @writeToSlice(ptr %s.ptr, i64 %s.len, i64 %s.cap)
%s.ptr2 = extractvalue { ptr, i64, i64 } %s, 0
%s.len2 = extractvalue { ptr, i64, i64 } %s, 1
%s.cap2 = extractvalue { ptr, i64, i64 } %s, 2
call fastcc void @printSlice(ptr %s.ptr2, i64 %s.len2, i64 %s.cap2)
ret void
}