Fix rare undefined asm temp end label error in x86

Summary:
Encountered assembly error due to undefined label `.LcaDcU_info_end` for
following code generated by `pprFrameProc`:

```
.Lsat_sa8fp{v}_info_fde_end:
  .long .Lblock{v caDcU}_info_fde_end-.Lblock{v caDcU}_info_fde
.Lblock{v caDcU}_info_fde:
  .long _nbHlD-.Lsection_frame
  .quad block{v caDcU}_info-1
  .quad .Lblock{v caDcU}_info_end-block{v caDcU}_info+1
  .byte 1
```

This diff fixed the error.

Test Plan:
  ./validate

Also the case where we used to have assembly error is now fixed.
Unfortunately, I have limited insight here and cannot get a small enough repro
or test case for this.

Ben says:

> I think I see: Previously we only produced end symbols for the info
> tables of top-level procedures. However, blocks within a procedure may
> also have info tables, we will dutifully generate debug information for
> and consequently we get undefined symbols.

Reviewers: simonmar, scpmw, last_g, bgamari

Reviewed By: bgamari

Subscribers: rwbarton, carter

Differential Revision: https://phabricator.haskell.org/D5246

(cherry picked from commit cf961dcf5ebc26cbd960196ba387736334088303)

1 files changed, 8 insertions, 7 deletions

diff --git a/compiler/nativeGen/X86/Ppr.hs b/compiler/nativeGen/X86/Ppr.hs
index c5fbeb544e..287ba031db 100644
--- a/compiler/nativeGen/X86/Ppr.hs
+++ b/compiler/nativeGen/X86/Ppr.hs
@@ -115,8 +115,6 @@ pprNatCmmDecl proc@(CmmProc top_info lbl _ (ListGraph blocks)) =
             <+> char '-'
             <+> ppr (mkDeadStripPreventer info_lbl)
        else empty) $$
-      (if debugLevel dflags > 0
-       then ppr (mkAsmTempEndLabel info_lbl) <> char ':' else empty) $$
       pprSizeDecl info_lbl
 
 -- | Output the ELF .size directive.
@@ -130,20 +128,23 @@ pprSizeDecl lbl
 pprBasicBlock :: LabelMap CmmStatics -> NatBasicBlock Instr -> SDoc
 pprBasicBlock info_env (BasicBlock blockid instrs)
   = sdocWithDynFlags $ \dflags ->
-    maybe_infotable $$
+    maybe_infotable dflags $
     pprLabel asmLbl $$
     vcat (map pprInstr instrs) $$
     (if debugLevel dflags > 0
      then ppr (mkAsmTempEndLabel asmLbl) <> char ':' else empty)
   where
     asmLbl = blockLbl blockid
-    maybe_infotable = case mapLookup blockid info_env of
-       Nothing   -> empty
-       Just (Statics info_lbl info) ->
+    maybe_infotable dflags c = case mapLookup blockid info_env of
+       Nothing -> c
+       Just (Statics infoLbl info) ->
            pprAlignForSection Text $$
            infoTableLoc $$
            vcat (map pprData info) $$
-           pprLabel info_lbl
+           pprLabel infoLbl $$
+           c $$
+           (if debugLevel dflags > 0
+            then ppr (mkAsmTempEndLabel infoLbl) <> char ':' else empty)
     -- Make sure the info table has the right .loc for the block
     -- coming right after it. See [Note: Info Offset]
     infoTableLoc = case instrs of