[llvm-commits] CVS: llvm/lib/Transforms/IPO/GlobalOpt.cpp

[Chris Lattner]

Changes in directory llvm/lib/Transforms/IPO:

GlobalOpt.cpp updated: 1.26 -> 1.27
---
Log message:

If a global is just loaded and restored, realize that it is not changing
value.  This allows us to turn more globals into constants and eliminate them.
This patch implements GlobalOpt/load-store-global.llx.

Note that this patch speeds up 255.vortex from:

Output/255.vortex.out-cbe.time:program 7.640000
Output/255.vortex.out-llc.time:program 9.810000

to:

Output/255.vortex.out-cbe.time:program 7.250000
Output/255.vortex.out-llc.time:program 9.490000

Which isn't bad at all!



---
Diffs of the changes:  (+9 -3)

Index: llvm/lib/Transforms/IPO/GlobalOpt.cpp
diff -u llvm/lib/Transforms/IPO/GlobalOpt.cpp:1.26 llvm/lib/Transforms/IPO/GlobalOpt.cpp:1.27
--- llvm/lib/Transforms/IPO/GlobalOpt.cpp:1.26	Fri Oct 22 01:43:28 2004
+++ llvm/lib/Transforms/IPO/GlobalOpt.cpp	Sun Nov 14 14:50:30 2004
@@ -155,14 +155,20 @@
         // stores.
         if (GS.StoredType != GlobalStatus::isStored)
           if (GlobalVariable *GV = dyn_cast<GlobalVariable>(SI->getOperand(1))){
-            if (SI->getOperand(0) == GV->getInitializer()) {
+            Value *StoredVal = SI->getOperand(0);
+            if (StoredVal == GV->getInitializer()) {
+              if (GS.StoredType < GlobalStatus::isInitializerStored)
+                GS.StoredType = GlobalStatus::isInitializerStored;
+            } else if (isa<LoadInst>(StoredVal) &&
+                       cast<LoadInst>(StoredVal)->getOperand(0) == GV) {
+              // G = G
               if (GS.StoredType < GlobalStatus::isInitializerStored)
                 GS.StoredType = GlobalStatus::isInitializerStored;
             } else if (GS.StoredType < GlobalStatus::isStoredOnce) {
               GS.StoredType = GlobalStatus::isStoredOnce;
-              GS.StoredOnceValue = SI->getOperand(0);
+              GS.StoredOnceValue = StoredVal;
             } else if (GS.StoredType == GlobalStatus::isStoredOnce &&
-                       GS.StoredOnceValue == SI->getOperand(0)) {
+                       GS.StoredOnceValue == StoredVal) {
               // noop.
             } else {
               GS.StoredType = GlobalStatus::isStored;