Have DataLayout::isLegalInteger accept a uint64_t

[mkuper]

Summary

Integer type sizes may have up to IntegerType::MAX_INT_BITS, which is currently 1<<23, so nothing that fits into an unsigned int will not be legal. However, having a uint64_t passed here avoids bugs due to truncation from uint64_t, as in PR26972.

Alternatively, we can require always checking for < UINT_MAX (or, better yet, for < MAX_INT_BITS) explicitly before calling DataLayout::isLegalInteger(), but that would make code like "DL.isLegalInteger(DL.getTypeSizeInBits(Ty))" (which we currently have in several places) wrong.

[mehdi_amini]

LGTM with a nit below.

include/llvm/IR/DataLayout.h

239 ↗

(On Diff #50989)

I guess the case where Width > MAX_INT_BITS is rare enough that it's not worth an early exit here?

test/Transforms/SROA/pr26972.ll

10 ↗

(On Diff #50989)

Add a comment specifying that this constant is intended to trigger 32 bits overflow.

[mkuper]

Thanks, Mehdi!

include/llvm/IR/DataLayout.h

239 ↗

(On Diff #50989)

Yeah, had the same thought, I think it's most probably not worth it.

test/Transforms/SROA/pr26972.ll

10 ↗

(On Diff #50989)

Right, thanks!

llvm/trunk/include/llvm/IR/DataLayout.h

public:
 
   /// \brief Returns true if the specified type is known to be a native integer
   /// type supported by the CPU.
   ///
   /// For example, i64 is not native on most 32-bit CPUs and i37 is not native
   /// on any known one. This returns false if the integer width is not legal.
   ///
   /// The width is specified in bits.
-  bool isLegalInteger(unsigned Width) const {
+  bool isLegalInteger(uint64_t Width) const {
     for (unsigned LegalIntWidth : LegalIntWidths)
       if (LegalIntWidth == Width)
         return true;
     return false;
   }
 
-  bool isIllegalInteger(unsigned Width) const { return !isLegalInteger(Width); }
+  bool isIllegalInteger(uint64_t Width) const { return !isLegalInteger(Width); }
 
   /// Returns true if the given alignment exceeds the natural stack alignment.
   bool exceedsNaturalStackAlignment(unsigned Align) const {
     return (StackNaturalAlign != 0) && (Align > StackNaturalAlign);
   }
 
   unsigned getStackAlignment() const { return StackNaturalAlign; }
 

llvm/trunk/test/Transforms/SROA/pr26972.ll

+; RUN: opt < %s -sroa -S | FileCheck %s
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-linux"
+
+; Make sure we properly handle allocas where the allocated
+; size overflows a uint32_t. This specific constant results in
+; the size in bits being 32 after truncation to a 32-bit int.
+; CHECK-LABEL: fn1
+; CHECK-NEXT: ret void
+define void @fn1() {
+  %a = alloca [1073741825 x i32], align 16
+  %t0 = bitcast [1073741825 x i32]* %a to i8*
+  call void @llvm.lifetime.end(i64 4294967300, i8* %t0)
+  ret void
+}
+
+declare void @llvm.lifetime.end(i64, i8* nocapture)