[PATCH] D22582: [AArch64] Load/store opt: Don't count transient instructions towards search limits.

[Geoff Berry via llvm-commits]

gberry created this revision.
gberry added a reviewer: mcrosier.
gberry added a subscriber: llvm-commits.
Herald added subscribers: mcrosier, rengolin, aemerson.

This change also changes findMatchingInsn and
findMatchingUpdateInsnForward to take DBG_VALUE opcodes into account
when tracking register defs and uses, which could potentially inhibit
these optimizations in the presence of debug information.

https://reviews.llvm.org/D22582

Files:
  lib/Target/AArch64/AArch64LoadStoreOptimizer.cpp

Index: lib/Target/AArch64/AArch64LoadStoreOptimizer.cpp
===================================================================
--- lib/Target/AArch64/AArch64LoadStoreOptimizer.cpp
+++ lib/Target/AArch64/AArch64LoadStoreOptimizer.cpp
@@ -1118,8 +1118,9 @@
     --MBBI;
     MachineInstr &MI = *MBBI;
 
-    // Don't count DBG_VALUE instructions towards the search limit.
-    if (!MI.isDebugValue())
+    // Don't count transient instructions towards the search limit since there
+    // may be different numbers of them if e.g. debug information is present.
+    if (!MI.isTransient())
       ++Count;
 
     // If the load instruction reads directly from the address to which the
@@ -1229,13 +1230,11 @@
 
   for (unsigned Count = 0; MBBI != E && Count < Limit; ++MBBI) {
     MachineInstr &MI = *MBBI;
-    // Skip DBG_VALUE instructions. Otherwise debug info can affect the
-    // optimization by changing how far we scan.
-    if (MI.isDebugValue())
-      continue;
 
-    // Now that we know this is a real instruction, count it.
-    ++Count;
+    // Don't count transient instructions towards the search limit since there
+    // may be different numbers of them if e.g. debug information is present.
+    if (!MI.isTransient())
+      ++Count;
 
     Flags.setSExtIdx(-1);
     if (areCandidatesToMergeOrPair(FirstMI, MI, Flags, TII) &&
@@ -1502,12 +1501,11 @@
   ++MBBI;
   for (unsigned Count = 0; MBBI != E && Count < Limit; ++MBBI) {
     MachineInstr &MI = *MBBI;
-    // Skip DBG_VALUE instructions.
-    if (MI.isDebugValue())
-      continue;
 
-    // Now that we know this is a real instruction, count it.
-    ++Count;
+    // Don't count transient instructions towards the search limit since there
+    // may be different numbers of them if e.g. debug information is present.
+    if (!MI.isTransient())
+      ++Count;
 
     // If we found a match, return it.
     if (isMatchingUpdateInsn(*I, MI, BaseReg, UnscaledOffset))
@@ -1556,8 +1554,9 @@
     --MBBI;
     MachineInstr &MI = *MBBI;
 
-    // Don't count DBG_VALUE instructions towards the search limit.
-    if (!MI.isDebugValue())
+    // Don't count transient instructions towards the search limit since there
+    // may be different numbers of them if e.g. debug information is present.
+    if (!MI.isTransient())
       ++Count;
 
     // If we found a match, return it.


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