[llvm] aa0b920 - [GlobalISel][IRTranslator] Move line zero DebugLoc creation to constant translation. NFC.

[Amara Emerson via llvm-commits]

Author: Amara Emerson
Date: 2021-04-28T23:54:14-07:00
New Revision: aa0b9200e8c5dea43c9ada2085a3061f4da70802

URL: https://github.com/llvm/llvm-project/commit/aa0b9200e8c5dea43c9ada2085a3061f4da70802
DIFF: https://github.com/llvm/llvm-project/commit/aa0b9200e8c5dea43c9ada2085a3061f4da70802.diff

LOG: [GlobalISel][IRTranslator] Move line zero DebugLoc creation to constant translation. NFC.

This is a compile time optimization. DILocation:get() is expensive to call, and
we were calling it to create a line zero debug loc for *every* instruction we
translated. We only really need to do this just before we build constants in the
entry block, so I moved this code there. This reduces the LLVM -O0 codegen time
of sqlite3 IR by around 0.7% instructions executed and by about ~2% in CPU time.

We can probably do better with a more involved change, since the reason we need
to create one for each new constant is because we're using the debug scope and
inlined-at loc. If we just use a single instruction's scope and drop the
inlined-at, we can just cache these and have them be free.

Added: 
    

Modified: 
    llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp

Removed: 
    


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diff  --git a/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp b/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
index 035b757e3c16..818c4c5e5567 100644
--- a/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
@@ -2842,13 +2842,6 @@ bool IRTranslator::valueIsSplit(const Value &V,
 
 bool IRTranslator::translate(const Instruction &Inst) {
   CurBuilder->setDebugLoc(Inst.getDebugLoc());
-  // We only emit constants into the entry block from here. To prevent jumpy
-  // debug behaviour set the line to 0.
-  if (const DebugLoc &DL = Inst.getDebugLoc())
-    EntryBuilder->setDebugLoc(DILocation::get(
-        Inst.getContext(), 0, 0, DL.getScope(), DL.getInlinedAt()));
-  else
-    EntryBuilder->setDebugLoc(DebugLoc());
 
   auto &TLI = *MF->getSubtarget().getTargetLowering();
   if (TLI.fallBackToDAGISel(Inst))
@@ -2865,6 +2858,15 @@ bool IRTranslator::translate(const Instruction &Inst) {
 }
 
 bool IRTranslator::translate(const Constant &C, Register Reg) {
+  // We only emit constants into the entry block from here. To prevent jumpy
+  // debug behaviour set the line to 0.
+  if (auto CurrInstDL = CurBuilder->getDL())
+    EntryBuilder->setDebugLoc(DILocation::get(C.getContext(), 0, 0,
+                                              CurrInstDL.getScope(),
+                                              CurrInstDL.getInlinedAt()));
+  else
+    EntryBuilder->setDebugLoc(DebugLoc());
+
   if (auto CI = dyn_cast<ConstantInt>(&C))
     EntryBuilder->buildConstant(Reg, *CI);
   else if (auto CF = dyn_cast<ConstantFP>(&C))