[clang] b0daacf - [CodeGen] Use llvm::bit_ceil (NFC)

[Kazu Hirata via cfe-commits]

Author: Kazu Hirata
Date: 2023-01-24T22:54:53-08:00
New Revision: b0daacf58f417634f7c7c9496589d723592a8f5a

URL: https://github.com/llvm/llvm-project/commit/b0daacf58f417634f7c7c9496589d723592a8f5a
DIFF: https://github.com/llvm/llvm-project/commit/b0daacf58f417634f7c7c9496589d723592a8f5a.diff

LOG: [CodeGen] Use llvm::bit_ceil (NFC)

If we know that x is nonzero and not a power of 2, then
llvm::findLastSet(x) + 1 is the index of the bit just above the
highest set bit in x.  That is, 1 << (llvm::findLastSet(x) + 1) is the
same as llvm::bit_ceil(x).

Since llvm::bit_ceil is a nop on a power of 2, we can unconditionally
call llvm::bit_ceil.  The end result actually matches the comment.

Added: 
    

Modified: 
    clang/lib/CodeGen/SwiftCallingConv.cpp

Removed: 
    


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diff  --git a/clang/lib/CodeGen/SwiftCallingConv.cpp b/clang/lib/CodeGen/SwiftCallingConv.cpp
index 6b868fe84ca68..63d975193c027 100644
--- a/clang/lib/CodeGen/SwiftCallingConv.cpp
+++ b/clang/lib/CodeGen/SwiftCallingConv.cpp
@@ -659,9 +659,7 @@ CharUnits swiftcall::getNaturalAlignment(CodeGenModule &CGM, llvm::Type *type) {
   // For Swift's purposes, this is always just the store size of the type
   // rounded up to a power of 2.
   auto size = (unsigned long long) getTypeStoreSize(CGM, type).getQuantity();
-  if (!isPowerOf2(size)) {
-    size = 1ULL << (llvm::findLastSet(size, llvm::ZB_Undefined) + 1);
-  }
+  size = llvm::bit_ceil(size);
   assert(CGM.getDataLayout().getABITypeAlign(type) <= size);
   return CharUnits::fromQuantity(size);
 }