[Issue 19550] New: [REG 2.078] Massive compiler backend slowdown

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=19550

          Issue ID: 19550
           Summary: [REG 2.078] Massive compiler backend slowdown
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: regression
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: ibuclaw at gdcproject.org

Test case:
---
# timeout 5 dmd -O bug.d
struct Buf
{
    char[7_000] buffer = void;
}

void main()
{
   uint len;

   auto b = Buf();
   b.buffer[len] = 'a';
}
---


In case you thought that the timeout of 5 seconds is too short, I compared
build times of the two releases in full.

 Compiler | Build time
----------------------
 2.077.1  | 0m0.527s
 2.078.0  | 1m3.694s

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