[PATCH] D57161: [RS4GC] Be slightly less conservative for gep vector_base, scalar_idx

[Philip Reames via Phabricator via llvm-commits]

reames created this revision.
reames added reviewers: anna, DaniilSuchkov.
Herald added subscribers: bollu, mcrosier.

After submitting https://reviews.llvm.org/D57138, I realized it was slightly more conservative than needed.  The scalar indices don't appear to be a problem on a scalar gep, we even had a test for that.


https://reviews.llvm.org/D57161

Files:
  lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
  test/Transforms/RewriteStatepointsForGC/base-vector.ll


Index: test/Transforms/RewriteStatepointsForGC/base-vector.ll
===================================================================
--- test/Transforms/RewriteStatepointsForGC/base-vector.ll
+++ test/Transforms/RewriteStatepointsForGC/base-vector.ll
@@ -253,7 +253,7 @@
 ; CHECK: @llvm.experimental.gc.statepoint.p0f_isVoidf{{.*}}<4 x i64 addrspace(1)*> %vec1)
 ; CHECK: %vec1.relocated = call coldcc <4 x i8 addrspace(1)*> @llvm.experimental.gc.relocate.v4p1i8
 ; CHECK: %vec1.relocated.casted = bitcast <4 x i8 addrspace(1)*> %vec1.relocated to <4 x i64 addrspace(1)*>
-; CHECK: %vec2.remat = getelementptr i64, <4 x i64 addrspace(1)*> %vec1.relocated.casted, <4 x i32> <i32 1024, i32 1024, i32 1024, i32 1024>
+; CHECK: %vec2.remat = getelementptr i64, <4 x i64 addrspace(1)*> %vec1.relocated.casted, i32 1024
 ; CHECK: call void @use_vec(<4 x i64 addrspace(1)*> %vec2.remat)
 entry:
   %vec2 = getelementptr i64, <4 x i64 addrspace(1)*> %vec1, i32 1024
Index: lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
===================================================================
--- lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
+++ lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
@@ -2611,21 +2611,20 @@
       continue;
 
     unsigned VF = 0;
-    bool HasScalarOperand = false;
     for (unsigned i = 0; i < I.getNumOperands(); i++)
-      if (I.getOperand(i)->getType()->isVectorTy())
+      if (I.getOperand(i)->getType()->isVectorTy()) {
+        assert(VF == 0 ||
+               VF == I.getOperand(i)->getType()->getVectorNumElements());
         VF = I.getOperand(i)->getType()->getVectorNumElements();
-      else
-        HasScalarOperand = true;
+      }
 
-    if (HasScalarOperand && VF != 0) {
+    // It's the vector to scalar traversal through the pointer operand which
+    // confuses base pointer rewriting, so limit ourselves to that case.
+    if (!I.getOperand(0)->getType()->isVectorTy() && VF != 0) {
       IRBuilder<> B(&I);
-      for (unsigned i = 0; i < I.getNumOperands(); i++)
-        if (!I.getOperand(i)->getType()->isVectorTy()) {
-          auto *Splat = B.CreateVectorSplat(VF, I.getOperand(i));
-          I.setOperand(i, Splat);
-          MadeChange = true;
-        }
+      auto *Splat = B.CreateVectorSplat(VF, I.getOperand(0));
+      I.setOperand(0, Splat);
+      MadeChange = true;
     }
   }
 


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