[llvm] [AsmPrinter] Fix emission in asm of alignment 2^32. (PR #98688)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-mc

Author: Eli Friedman (efriedma-quic)

<details>
<summary>Changes</summary>

The alignment amount was getting corrupted due to accidental truncation.

---
Full diff: https://github.com/llvm/llvm-project/pull/98688.diff


2 Files Affected:

- (modified) llvm/lib/MC/MCAsmStreamer.cpp (+6-6) 
- (added) llvm/test/CodeGen/X86/global-with-max-align.ll (+14) 


``````````diff
diff --git a/llvm/lib/MC/MCAsmStreamer.cpp b/llvm/lib/MC/MCAsmStreamer.cpp
index 45c32f13e759b..24209e456b5e2 100644
--- a/llvm/lib/MC/MCAsmStreamer.cpp
+++ b/llvm/lib/MC/MCAsmStreamer.cpp
@@ -254,7 +254,7 @@ class MCAsmStreamer final : public MCStreamer {
   void emitFill(const MCExpr &NumValues, int64_t Size, int64_t Expr,
                 SMLoc Loc = SMLoc()) override;
 
-  void emitAlignmentDirective(unsigned ByteAlignment,
+  void emitAlignmentDirective(uint64_t ByteAlignment,
                               std::optional<int64_t> Value, unsigned ValueSize,
                               unsigned MaxBytesToEmit);
 
@@ -1478,23 +1478,23 @@ void MCAsmStreamer::emitFill(const MCExpr &NumValues, int64_t Size,
   EmitEOL();
 }
 
-void MCAsmStreamer::emitAlignmentDirective(unsigned ByteAlignment,
+void MCAsmStreamer::emitAlignmentDirective(uint64_t ByteAlignment,
                                            std::optional<int64_t> Value,
                                            unsigned ValueSize,
                                            unsigned MaxBytesToEmit) {
   if (MAI->useDotAlignForAlignment()) {
-    if (!isPowerOf2_32(ByteAlignment))
+    if (!isPowerOf2_64(ByteAlignment))
       report_fatal_error("Only power-of-two alignments are supported "
                          "with .align.");
     OS << "\t.align\t";
-    OS << Log2_32(ByteAlignment);
+    OS << Log2_64(ByteAlignment);
     EmitEOL();
     return;
   }
 
   // Some assemblers don't support non-power of two alignments, so we always
   // emit alignments as a power of two if possible.
-  if (isPowerOf2_32(ByteAlignment)) {
+  if (isPowerOf2_64(ByteAlignment)) {
     switch (ValueSize) {
     default:
       llvm_unreachable("Invalid size for machine code value!");
@@ -1511,7 +1511,7 @@ void MCAsmStreamer::emitAlignmentDirective(unsigned ByteAlignment,
       llvm_unreachable("Unsupported alignment size!");
     }
 
-    OS << Log2_32(ByteAlignment);
+    OS << Log2_64(ByteAlignment);
 
     if (Value.has_value() || MaxBytesToEmit) {
       if (Value.has_value()) {
diff --git a/llvm/test/CodeGen/X86/global-with-max-align.ll b/llvm/test/CodeGen/X86/global-with-max-align.ll
new file mode 100644
index 0000000000000..76617abaae5f6
--- /dev/null
+++ b/llvm/test/CodeGen/X86/global-with-max-align.ll
@@ -0,0 +1,14 @@
+; RUN: llc -mtriple=x86_64 < %s | FileCheck %s
+
+; CHECK: .globl  g1
+; CHECK-NEXT: .p2align 32, 0x0
+; CHECK: .globl  g2
+; CHECK-NEXT: .p2align 32, 0x0
+; CHECK: .globl  g3
+; CHECK-NEXT: .p2align 32, 0x0
+
+; OBJ: ZZZ
+
+ at g1 = global i32 0, align 4294967296
+ at g2 = global i32 33, align 4294967296
+ at g3 = constant i32 44, align 4294967296

``````````

</details>


https://github.com/llvm/llvm-project/pull/98688