[flang-commits] [flang] 03cef62 - [flang][NFC] turn (h)fir.declare side effect into debug ressource alloca (#113321)

[via flang-commits]

Author: jeanPerier
Date: 2024-10-23T12:33:34+02:00
New Revision: 03cef62fe53d9927865f2acbde438fc35377f16e

URL: https://github.com/llvm/llvm-project/commit/03cef62fe53d9927865f2acbde438fc35377f16e
DIFF: https://github.com/llvm/llvm-project/commit/03cef62fe53d9927865f2acbde438fc35377f16e.diff

LOG: [flang][NFC] turn (h)fir.declare side effect into debug ressource alloca (#113321)

See https://reviews.llvm.org/D157626 for the rational of declare having
side effects.

The write effect is to scary for passes that look for read/write effects
without caring about the resource affected. I know Slava asked for it,
but I think the creation of the `DebuggingResource` was enough and that
a write is too much. The alloca effect is sufficient to prevent DCE to
remove it, which is all we care about currently.

This currently is flag as a reason for creating LHS temporary in
assignment to vector subscripted entity with array constructor.
There is a lot of read/write side effect analysis in the
"lower-hlfir-ordered-assignments" pass, and I feel like we will just
keep adding weird "debug ressource" bypassing here and there with these
side effects.

Added: 
    

Modified: 
    flang/include/flang/Optimizer/Dialect/FIROps.td
    flang/include/flang/Optimizer/HLFIR/HLFIROps.td

Removed: 
    


################################################################################
diff  --git a/flang/include/flang/Optimizer/Dialect/FIROps.td b/flang/include/flang/Optimizer/Dialect/FIROps.td
index d467f0ab4e1c1e..eda8f26e936fb6 100644
--- a/flang/include/flang/Optimizer/Dialect/FIROps.td
+++ b/flang/include/flang/Optimizer/Dialect/FIROps.td
@@ -3078,7 +3078,7 @@ def fir_IsPresentOp : fir_SimpleOp<"is_present", [NoMemoryEffect]> {
 // debug information so we would like to keep this around even if the value
 // is not used.
 def fir_DeclareOp : fir_Op<"declare", [AttrSizedOperandSegments,
-    MemoryEffects<[MemWrite<DebuggingResource>]>,
+    MemoryEffects<[MemAlloc<DebuggingResource>]>,
     DeclareOpInterfaceMethods<fir_FortranVariableOpInterface>]> {
   let summary = "declare a variable";
 

diff  --git a/flang/include/flang/Optimizer/HLFIR/HLFIROps.td b/flang/include/flang/Optimizer/HLFIR/HLFIROps.td
index b162af55d66bb4..1ab8793f726523 100644
--- a/flang/include/flang/Optimizer/HLFIR/HLFIROps.td
+++ b/flang/include/flang/Optimizer/HLFIR/HLFIROps.td
@@ -36,7 +36,7 @@ class hlfir_Op<string mnemonic, list<Trait> traits>
 // from the declare operation can be used to generate debug information so we
 // don't want to remove it as dead code
 def hlfir_DeclareOp : hlfir_Op<"declare", [AttrSizedOperandSegments,
-    MemoryEffects<[MemWrite<DebuggingResource>]>,
+    MemoryEffects<[MemAlloc<DebuggingResource>]>,
     DeclareOpInterfaceMethods<fir_FortranVariableOpInterface>]> {
   let summary = "declare a variable and produce an SSA value that can be used as a variable in HLFIR operations";