[PATCH] D82761: SpeculativeExecution: Fix for logic change introduced in D81730.

[Daniil Fukalov via Phabricator via llvm-commits]

dfukalov created this revision.
dfukalov added reviewers: aprantl, arsenm, nhaehnle.
Herald added subscribers: hiraditya, wdng.
Herald added a project: LLVM.

The test case started to hoist bitcasts to upper BB after D81730 <https://reviews.llvm.org/D81730>.
Reverted unintentional logic change. Some instructions may have zero cost but
will not be hoisted by different limitation so should be counted for threshold.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D82761

Files:
  llvm/lib/Transforms/Scalar/SpeculativeExecution.cpp
  llvm/test/Transforms/SpeculativeExecution/PR46267.ll


Index: llvm/test/Transforms/SpeculativeExecution/PR46267.ll
===================================================================
--- llvm/test/Transforms/SpeculativeExecution/PR46267.ll
+++ llvm/test/Transforms/SpeculativeExecution/PR46267.ll
@@ -1,6 +1,35 @@
 ; RUN: opt < %s -S -speculative-execution | FileCheck %s
 ; RUN: opt < %s -S -passes='speculative-execution' | FileCheck %s
 
+%class.B = type { i32 (...)** }
+
+define i8* @_Z9void_castP1B(%class.B* readonly %b) {
+; CHECK-LABEL: _Z9void_castP1B
+; CHECK-LABEL: entry
+; CHECK-NEXT: %i = icmp eq %class.B* %b, null
+; CHECK-NEXT: br i1 %i, label %dynamic_cast.end, label %dynamic_cast.notnull
+entry:
+  %i = icmp eq %class.B* %b, null
+  br i1 %i, label %dynamic_cast.end, label %dynamic_cast.notnull
+
+; CHECK-LABEL: dynamic_cast.notnull:
+; CHECK-NEXT: %i1 = bitcast %class.B* %b to i32**
+; CHECK: %i3 = bitcast %class.B* %b to i8*
+dynamic_cast.notnull:                             ; preds = %entry
+  %i1 = bitcast %class.B* %b to i32**
+  %vtable = load i32*, i32** %i1, align 8
+  %i2 = getelementptr inbounds i32, i32* %vtable, i64 -2
+  %offset.to.top = load i32, i32* %i2, align 4
+  %i3 = bitcast %class.B* %b to i8*
+  %i4 = sext i32 %offset.to.top to i64
+  %i5 = getelementptr inbounds i8, i8* %i3, i64 %i4
+  br label %dynamic_cast.end
+
+dynamic_cast.end:                                 ; preds = %dynamic_cast.notnull, %entry
+  %i6 = phi i8* [ %i5, %dynamic_cast.notnull ], [ null, %entry ]
+  ret i8* %i6
+}
+
 define void @f(i32 %i) {
 entry:
 ; CHECK-LABEL: @f(
Index: llvm/lib/Transforms/Scalar/SpeculativeExecution.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/SpeculativeExecution.cpp
+++ llvm/lib/Transforms/Scalar/SpeculativeExecution.cpp
@@ -291,10 +291,8 @@
       if (TotalSpeculationCost > SpecExecMaxSpeculationCost)
         return false;  // too much to hoist
     } else {
-      // If the instruction cannot be hoisted but has zero cost suppose it's
-      // a special case e.g. debug info instrinsics that should not be counted
-      // for threshold.
-      if (Cost)
+      // Debug info instrinsics should not be counted for threshold.
+      if (!isa<DbgInfoIntrinsic>(I))
         NotHoistedInstCount++;
       if (NotHoistedInstCount > SpecExecMaxNotHoisted)
         return false; // too much left behind


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