[llvm] fb7caa3 - [AsmPrinter] Reject ptrtoint to larger size in lowerConstant()

[Nikita Popov via llvm-commits]

Author: Nikita Popov
Date: 2022-07-25T10:18:27+02:00
New Revision: fb7caa3c7b53a4362139afe0158f297a891cc17b

URL: https://github.com/llvm/llvm-project/commit/fb7caa3c7b53a4362139afe0158f297a891cc17b
DIFF: https://github.com/llvm/llvm-project/commit/fb7caa3c7b53a4362139afe0158f297a891cc17b.diff

LOG: [AsmPrinter] Reject ptrtoint to larger size in lowerConstant()

When using a ptrtoint to a size larger than the pointer width in a
global initializer, we currently create a ptr & low_bit_mask style
MCExpr, which will later result in a relocation error during object
file emission.

This patch rejects the constant expression already during
lowerConstant(), which results in a much clearer error message
that references the constant expression at fault.

This fixes https://github.com/llvm/llvm-project/issues/56400,
for certain definitions of "fix".

Differential Revision: https://reviews.llvm.org/D130366

Added: 
    llvm/test/CodeGen/X86/ptrtoint-constexpr-invalid.ll

Modified: 
    llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
    llvm/test/CodeGen/X86/ptrtoint-constexpr.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index e0050a47a6f6b..32a10ad41d1fd 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -2795,12 +2795,7 @@ const MCExpr *AsmPrinter::lowerConstant(const Constant *CV) {
         DL.getTypeAllocSize(Op->getType()).getFixedSize())
       return OpExpr;
 
-    // Otherwise the pointer is smaller than the resultant integer, mask off
-    // the high bits so we are sure to get a proper truncation if the input is
-    // a constant expr.
-    unsigned InBits = DL.getTypeAllocSizeInBits(Op->getType());
-    const MCExpr *MaskExpr = MCConstantExpr::create(~0ULL >> (64-InBits), Ctx);
-    return MCBinaryExpr::createAnd(OpExpr, MaskExpr, Ctx);
+    break; // Error
   }
 
   case Instruction::Sub: {

diff  --git a/llvm/test/CodeGen/X86/ptrtoint-constexpr-invalid.ll b/llvm/test/CodeGen/X86/ptrtoint-constexpr-invalid.ll
new file mode 100644
index 0000000000000..f1f5d7e2b7204
--- /dev/null
+++ b/llvm/test/CodeGen/X86/ptrtoint-constexpr-invalid.ll
@@ -0,0 +1,10 @@
+; RUN: not --crash llc < %s -mtriple=i386-linux 2>&1 | FileCheck %s
+
+; ptrtoint expressions that cast to a wider integer type are not supported.
+; A frontend can achieve a similar result by casting to the correct integer
+; type and explicitly zeroing any additional bytes.
+; { i32, i32 } { i32 ptrtoint (ptr @r to i32), i32 0 }
+
+; CHECK: LLVM ERROR: Unsupported expression in static initializer: ptrtoint (ptr @r to i64)
+
+ at r = global i64 ptrtoint (ptr @r to i64)

diff  --git a/llvm/test/CodeGen/X86/ptrtoint-constexpr.ll b/llvm/test/CodeGen/X86/ptrtoint-constexpr.ll
index 15ad13022235a..58d1895f0b158 100644
--- a/llvm/test/CodeGen/X86/ptrtoint-constexpr.ll
+++ b/llvm/test/CodeGen/X86/ptrtoint-constexpr.ll
@@ -1,11 +1,11 @@
 ; RUN: llc < %s -mtriple=i386-linux | FileCheck %s
-	%union.x = type { i64 }
+	%union.x = type { i32 }
 
 ; CHECK:	.globl r
 ; CHECK: r:
-; CHECK: .quad	r&4294967295
+; CHECK: .long	r
 
- at r = global %union.x { i64 ptrtoint (ptr @r to i64) }, align 4
+ at r = global %union.x { i32 ptrtoint (ptr @r to i32) }, align 4
 
 ; CHECK:	.globl x
 ; CHECK: x: