make GVN work better when TD is not around:

"In the existing code, if the load and the value to replace it with are
of different types *and* target data is available, it tries to use the
target data to coerce the replacement value to the type of the load.
Otherwise, it skips all effort to handle the type mismatch and just
feeds the wrongly-typed replacement value to replaceAllUsesWith, which
triggers an assertion.

The patch replaces it with an outer if checking for type mismatch, and
an inner if-else that checks whether target data is available and, if
not, returns false rather than trying to replace the load."

Patch by Kenneth Uildriks!



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@84739 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 21 insertions, 15 deletions

diff --git a/lib/Transforms/Scalar/GVN.cpp b/lib/Transforms/Scalar/GVN.cpp
index ef6c3389c9..8859324914 100644
--- a/lib/Transforms/Scalar/GVN.cpp
+++ b/lib/Transforms/Scalar/GVN.cpp
@@ -1530,15 +1530,18 @@ bool GVN::processLoad(LoadInst *L, SmallVectorImpl<Instruction*> &toErase) {
     // actually have the same type.  See if we know how to reuse the stored
     // value (depending on its type).
     const TargetData *TD = 0;
-    if (StoredVal->getType() != L->getType() &&
-        (TD = getAnalysisIfAvailable<TargetData>())) {
-      StoredVal = CoerceAvailableValueToLoadType(StoredVal, L->getType(),
-                                                 L, *TD);
-      if (StoredVal == 0)
+    if (StoredVal->getType() != L->getType()) {
+      if ((TD = getAnalysisIfAvailable<TargetData>())) {
+        StoredVal = CoerceAvailableValueToLoadType(StoredVal, L->getType(),
+                                                   L, *TD);
+        if (StoredVal == 0)
+          return false;
+        
+        DEBUG(errs() << "GVN COERCED STORE:\n" << *DepSI << '\n' << *StoredVal
+                     << '\n' << *L << "\n\n\n");
+      }
+      else 
         return false;
-      
-      DEBUG(errs() << "GVN COERCED STORE:\n" << *DepSI << '\n' << *StoredVal
-                   << '\n' << *L << "\n\n\n");
     }
 
     // Remove it!
@@ -1557,14 +1560,17 @@ bool GVN::processLoad(LoadInst *L, SmallVectorImpl<Instruction*> &toErase) {
     // the same type.  See if we know how to reuse the previously loaded value
     // (depending on its type).
     const TargetData *TD = 0;
-    if (DepLI->getType() != L->getType() &&
-        (TD = getAnalysisIfAvailable<TargetData>())) {
-      AvailableVal = CoerceAvailableValueToLoadType(DepLI, L->getType(), L,*TD);
-      if (AvailableVal == 0)
-        return false;
+    if (DepLI->getType() != L->getType()) {
+      if ((TD = getAnalysisIfAvailable<TargetData>())) {
+        AvailableVal = CoerceAvailableValueToLoadType(DepLI, L->getType(), L,*TD);
+        if (AvailableVal == 0)
+          return false;
       
-      DEBUG(errs() << "GVN COERCED LOAD:\n" << *DepLI << "\n" << *AvailableVal
-                   << "\n" << *L << "\n\n\n");
+        DEBUG(errs() << "GVN COERCED LOAD:\n" << *DepLI << "\n" << *AvailableVal
+                     << "\n" << *L << "\n\n\n");
+      }
+      else 
+        return false;
     }
     
     // Remove it!