[clang] 0858f0e - [SystemZ][z/OS] Set maximum value to truncate attribute aligned to for static variables on z/OS target

[Fanbo Meng via cfe-commits]

Author: Fanbo Meng
Date: 2021-03-29T09:44:33-04:00
New Revision: 0858f0e09e33f62fc1dcc45e0bdec47eee1e23ba

URL: https://github.com/llvm/llvm-project/commit/0858f0e09e33f62fc1dcc45e0bdec47eee1e23ba
DIFF: https://github.com/llvm/llvm-project/commit/0858f0e09e33f62fc1dcc45e0bdec47eee1e23ba.diff

LOG: [SystemZ][z/OS] Set maximum value to truncate attribute aligned to for static variables on z/OS target

On z/OS there is a hard limitation on on the maximum requestable alignment in aligned attribute for static variables. We need to truncate values greater than that.

Reviewed By: abhina.sreeskantharajan

Differential Revision: https://reviews.llvm.org/D98864

Added: 
    

Modified: 
    clang/include/clang/Basic/TargetInfo.h
    clang/lib/AST/ASTContext.cpp
    clang/lib/Basic/TargetInfo.cpp
    clang/lib/Basic/Targets/OSTargets.h
    clang/test/CodeGen/SystemZ/zos-alignment.c

Removed: 
    


################################################################################
diff  --git a/clang/include/clang/Basic/TargetInfo.h b/clang/include/clang/Basic/TargetInfo.h
index 01ca9ca0d2a8..3ddb706dcf52 100644
--- a/clang/include/clang/Basic/TargetInfo.h
+++ b/clang/include/clang/Basic/TargetInfo.h
@@ -165,6 +165,10 @@ struct TransferrableTargetInfo {
   /// If non-zero, specifies a fixed alignment value for bitfields that follow
   /// zero length bitfield, regardless of the zero length bitfield type.
   unsigned ZeroLengthBitfieldBoundary;
+
+  /// If non-zero, specifies a maximum alignment to truncate alignment
+  /// specified in the aligned attribute of a static variable to this value.
+  unsigned MaxAlignedAttribute;
 };
 
 /// OpenCL type kinds.
@@ -784,6 +788,10 @@ class TargetInfo : public virtual TransferrableTargetInfo,
     return ZeroLengthBitfieldBoundary;
   }
 
+  /// Get the maximum alignment in bits for a static variable with
+  /// aligned attribute.
+  unsigned getMaxAlignedAttribute() const { return MaxAlignedAttribute; }
+
   /// Check whether explicit bitfield alignment attributes should be
   //  honored, as in "__attribute__((aligned(2))) int b : 1;".
   bool useExplicitBitFieldAlignment() const {

diff  --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index d52aea88e092..c824bcfa0866 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -1783,6 +1783,13 @@ CharUnits ASTContext::getDeclAlign(const Decl *D, bool ForAlignof) const {
     }
   }
 
+  // Some targets have hard limitation on the maximum requestable alignment in
+  // aligned attribute for static variables.
+  const unsigned MaxAlignedAttr = getTargetInfo().getMaxAlignedAttribute();
+  const auto *VD = dyn_cast<VarDecl>(D);
+  if (MaxAlignedAttr && VD && VD->getStorageClass() == SC_Static)
+    Align = std::min(Align, MaxAlignedAttr);
+
   return toCharUnitsFromBits(Align);
 }
 

diff  --git a/clang/lib/Basic/TargetInfo.cpp b/clang/lib/Basic/TargetInfo.cpp
index 468c8a24498a..1783da8f9cfd 100644
--- a/clang/lib/Basic/TargetInfo.cpp
+++ b/clang/lib/Basic/TargetInfo.cpp
@@ -107,6 +107,7 @@ TargetInfo::TargetInfo(const llvm::Triple &T) : TargetOpts(), Triple(T) {
   UseLeadingZeroLengthBitfield = true;
   UseExplicitBitFieldAlignment = true;
   ZeroLengthBitfieldBoundary = 0;
+  MaxAlignedAttribute = 0;
   HalfFormat = &llvm::APFloat::IEEEhalf();
   FloatFormat = &llvm::APFloat::IEEEsingle();
   DoubleFormat = &llvm::APFloat::IEEEdouble();

diff  --git a/clang/lib/Basic/Targets/OSTargets.h b/clang/lib/Basic/Targets/OSTargets.h
index 568f759bfa0d..6e757adfa8bf 100644
--- a/clang/lib/Basic/Targets/OSTargets.h
+++ b/clang/lib/Basic/Targets/OSTargets.h
@@ -794,6 +794,7 @@ class LLVM_LIBRARY_VISIBILITY ZOSTargetInfo : public OSTargetInfo<Target> {
   ZOSTargetInfo(const llvm::Triple &Triple, const TargetOptions &Opts)
       : OSTargetInfo<Target>(Triple, Opts) {
     this->WCharType = TargetInfo::UnsignedInt;
+    this->MaxAlignedAttribute = 128;
     this->UseBitFieldTypeAlignment = false;
     this->UseZeroLengthBitfieldAlignment = true;
     this->UseLeadingZeroLengthBitfield = false;

diff  --git a/clang/test/CodeGen/SystemZ/zos-alignment.c b/clang/test/CodeGen/SystemZ/zos-alignment.c
index 703fd1a46c3b..9371a54403e4 100644
--- a/clang/test/CodeGen/SystemZ/zos-alignment.c
+++ b/clang/test/CodeGen/SystemZ/zos-alignment.c
@@ -1,4 +1,16 @@
-// RUN: %clang_cc1 -emit-llvm-only -triple s390x-none-zos -fdump-record-layouts %s | FileCheck %s
+// RUN: %clang_cc1 -emit-llvm-only -triple s390x-none-zos -fdump-record-layouts %s | FileCheck %s --check-prefix=CHECK
+// RUN: %clang_cc1 -emit-llvm -triple s390x-none-zos %s -o - | FileCheck %s --check-prefix=DECL
+
+static int __attribute__((aligned(32))) v0;
+int __attribute__((aligned(32))) v1;
+typedef int __attribute__((aligned(32))) int32;
+static int32 v2;
+int32 v3;
+int f0() { return v0 + v1 + v2 + v3; }
+// DECL:      @v0 {{.*}} align 16
+// DECL-NEXT: @v1 {{.*}} align 32
+// DECL-NEXT: @v2 {{.*}} align 16
+// DECL-NEXT: @v3 {{.*}} align 32
 
 struct s0 {
   short a:3;