[clang] Revert "[X86][clang] Lift _BitInt() supported max width." (PR #81175)

[Harald van Dijk via cfe-commits]

https://github.com/hvdijk created https://github.com/llvm/llvm-project/pull/81175

This reverts commit def720726b73e0d7ab139376ab3ea955f25f4d89.

As noted in #60925 and in D86310, with the current implementation of `_BitInt` in Clang, we can have either a correct `__int128` implementation, or a correct `_BitInt(128)` implementation, but not both: having a correct `__int128` implementation results in a mostly-working `_BitInt(65-128)` type, but internal compiler errors and seriously wrong code for `_BitInt(129+)`. The currently specified ABI is not implementable on top of LLVM's integer types, and attempts to get the ABI changed to something we can implement have resulted in nothing, so I think the safest thing to do at this time is to make sure Clang reports this as an error in exactly the same way that it does for all other architectures. I think it was simply too soon to lift that restriction.

cc @FreddyLeaf 

>From 7b8f198b3bb00ca0624e7de061a977e1d3b87c00 Mon Sep 17 00:00:00 2001
From: Harald van Dijk <harald at gigawatt.nl>
Date: Thu, 8 Feb 2024 19:06:14 +0000
Subject: [PATCH] Revert "[X86][clang] Lift _BitInt() supported max width."

This reverts commit def720726b73e0d7ab139376ab3ea955f25f4d89.
---
 clang/docs/ReleaseNotes.rst           |  2 ++
 clang/lib/Basic/Targets/X86.h         |  6 ------
 clang/test/Analysis/bitint-no-crash.c |  5 ++---
 clang/test/CodeGen/ext-int-cc.c       | 16 ++++++++--------
 4 files changed, 12 insertions(+), 17 deletions(-)

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 32440ee64e3eb..a52e0c0112ba2 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -239,6 +239,8 @@ AMDGPU Support
 X86 Support
 ^^^^^^^^^^^
 
+- Revert _BitInt() supported max width increase, which does not work properly.
+
 Arm and AArch64 Support
 ^^^^^^^^^^^^^^^^^^^^^^^
 
diff --git a/clang/lib/Basic/Targets/X86.h b/clang/lib/Basic/Targets/X86.h
index d2232c7d5275a..7010c1fbb5a4e 100644
--- a/clang/lib/Basic/Targets/X86.h
+++ b/clang/lib/Basic/Targets/X86.h
@@ -507,9 +507,6 @@ class LLVM_LIBRARY_VISIBILITY X86_32TargetInfo : public X86TargetInfo {
   ArrayRef<Builtin::Info> getTargetBuiltins() const override;
 
   bool hasBitIntType() const override { return true; }
-  size_t getMaxBitIntWidth() const override {
-    return llvm::IntegerType::MAX_INT_BITS;
-  }
 };
 
 class LLVM_LIBRARY_VISIBILITY NetBSDI386TargetInfo
@@ -820,9 +817,6 @@ class LLVM_LIBRARY_VISIBILITY X86_64TargetInfo : public X86TargetInfo {
   ArrayRef<Builtin::Info> getTargetBuiltins() const override;
 
   bool hasBitIntType() const override { return true; }
-  size_t getMaxBitIntWidth() const override {
-    return llvm::IntegerType::MAX_INT_BITS;
-  }
 };
 
 // x86-64 Windows target
diff --git a/clang/test/Analysis/bitint-no-crash.c b/clang/test/Analysis/bitint-no-crash.c
index 0a367fa930dc9..aa9bd61e7e421 100644
--- a/clang/test/Analysis/bitint-no-crash.c
+++ b/clang/test/Analysis/bitint-no-crash.c
@@ -1,10 +1,9 @@
  // RUN: %clang_analyze_cc1 -analyzer-checker=core \
  // RUN:   -analyzer-checker=debug.ExprInspection \
- // RUN:   -triple x86_64-pc-linux-gnu \
+ // RUN:   -fexperimental-max-bitint-width=256 \
  // RUN:   -verify %s
 
-// Don't crash when using _BitInt(). Pin to the x86_64 triple for now,
-// since not all architectures support _BitInt()
+// Don't crash when using _BitInt().
 // expected-no-diagnostics
 _BitInt(256) a;
 _BitInt(129) b;
diff --git a/clang/test/CodeGen/ext-int-cc.c b/clang/test/CodeGen/ext-int-cc.c
index 001e866d34b45..b233285ea36da 100644
--- a/clang/test/CodeGen/ext-int-cc.c
+++ b/clang/test/CodeGen/ext-int-cc.c
@@ -131,10 +131,10 @@ void ParamPassing3(_BitInt(15) a, _BitInt(31) b) {}
 // are negated. This will give an error when a target does support larger
 // _BitInt widths to alert us to enable the test.
 void ParamPassing4(_BitInt(129) a) {}
-// LIN64: define{{.*}} void @ParamPassing4(ptr byval(i129) align 8 %{{.+}})
-// WIN64: define dso_local void @ParamPassing4(ptr %{{.+}})
-// LIN32: define{{.*}} void @ParamPassing4(ptr %{{.+}})
-// WIN32: define dso_local void @ParamPassing4(ptr %{{.+}})
+// LIN64-NOT: define{{.*}} void @ParamPassing4(ptr byval(i129) align 8 %{{.+}})
+// WIN64-NOT: define dso_local void @ParamPassing4(ptr %{{.+}})
+// LIN32-NOT: define{{.*}} void @ParamPassing4(ptr %{{.+}})
+// WIN32-NOT: define dso_local void @ParamPassing4(ptr %{{.+}})
 // NACL-NOT: define{{.*}} void @ParamPassing4(ptr byval(i129) align 8 %{{.+}})
 // NVPTX64-NOT: define{{.*}} void @ParamPassing4(ptr byval(i129) align 8 %{{.+}})
 // NVPTX-NOT: define{{.*}} void @ParamPassing4(ptr byval(i129) align 8 %{{.+}})
@@ -290,10 +290,10 @@ _BitInt(128) ReturnPassing4(void){}
 
 #if __BITINT_MAXWIDTH__ > 128
 _BitInt(129) ReturnPassing5(void){}
-// LIN64: define{{.*}} void @ReturnPassing5(ptr dead_on_unwind noalias writable sret
-// WIN64: define dso_local void @ReturnPassing5(ptr dead_on_unwind noalias writable sret
-// LIN32: define{{.*}} void @ReturnPassing5(ptr dead_on_unwind noalias writable sret
-// WIN32: define dso_local void @ReturnPassing5(ptr dead_on_unwind noalias writable sret
+// LIN64-NOT: define{{.*}} void @ReturnPassing5(ptr dead_on_unwind noalias writable sret
+// WIN64-NOT: define dso_local void @ReturnPassing5(ptr dead_on_unwind noalias writable sret
+// LIN32-NOT: define{{.*}} void @ReturnPassing5(ptr dead_on_unwind noalias writable sret
+// WIN32-NOT: define dso_local void @ReturnPassing5(ptr dead_on_unwind noalias writable sret
 // NACL-NOT: define{{.*}} void @ReturnPassing5(ptr dead_on_unwind noalias writable sret
 // NVPTX64-NOT: define{{.*}} i129 @ReturnPassing5(
 // NVPTX-NOT: define{{.*}} i129 @ReturnPassing5(