[llvm] e45b070 - [DebugInfo] Fixing CodeView assert related to lowerBound field of DISubrange.

[Sourabh Singh Tomar via llvm-commits]

Author: Alok Kumar Sharma
Date: 2020-09-11T11:12:49+05:30
New Revision: e45b0708ae81ace27de53f12b32a80601cb12bf3

URL: https://github.com/llvm/llvm-project/commit/e45b0708ae81ace27de53f12b32a80601cb12bf3
DIFF: https://github.com/llvm/llvm-project/commit/e45b0708ae81ace27de53f12b32a80601cb12bf3.diff

LOG: [DebugInfo] Fixing CodeView assert related to lowerBound field of DISubrange.

    This is to fix CodeView build failure https://bugs.llvm.org/show_bug.cgi?id=47287
    after DIsSubrange upgrade D80197

    Assert condition is now removed and Count is calculated in case LowerBound
    is absent or zero and Count or UpperBound is constant. If Count is unknown
    it is later handled as VLA (currently Count is set to zero).

Reviewed By: rnk

Differential Revision: https://reviews.llvm.org/D87406

Added: 
    

Modified: 
    llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp

Removed: 
    


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diff  --git a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
index b388e4344783..bcace6264cd0 100644
--- a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
@@ -1578,11 +1578,16 @@ TypeIndex CodeViewDebug::lowerTypeArray(const DICompositeType *Ty) {
     assert(Element->getTag() == dwarf::DW_TAG_subrange_type);
 
     const DISubrange *Subrange = cast<DISubrange>(Element);
-    assert(!Subrange->getRawLowerBound() &&
-           "codeview doesn't support subranges with lower bounds");
     int64_t Count = -1;
-    if (auto *CI = Subrange->getCount().dyn_cast<ConstantInt*>())
-      Count = CI->getSExtValue();
+    // Calculate the count if either LowerBound is absent or is zero and
+    // either of Count or UpperBound are constant.
+    auto *LI = Subrange->getLowerBound().dyn_cast<ConstantInt *>();
+    if (!Subrange->getRawLowerBound() || (LI && (LI->getSExtValue() == 0))) {
+      if (auto *CI = Subrange->getCount().dyn_cast<ConstantInt*>())
+        Count = CI->getSExtValue();
+      else if (auto *UI = Subrange->getUpperBound().dyn_cast<ConstantInt*>())
+        Count = UI->getSExtValue() + 1; // LowerBound is zero
+    }
 
     // Forward declarations of arrays without a size and VLAs use a count of -1.
     // Emit a count of zero in these cases to match what MSVC does for arrays