Replace LLVMConstInBoundsGEP with LLVMConstInBoundsGEP2*

A custom reimplementation of LLVMConstInBoundsGEP2 is used, since the
LLVM contains a declaration of LLVMConstInBoundsGEP2 but not the
implementation.

Author: tmiasko

compiler/rustc_codegen_llvm/src/common.rs

@@ -268,7 +268,8 @@ impl ConstMethods<'tcx> for CodegenCx<'ll, 'tcx> {
                     }
                 };
                 let llval = unsafe {
-                    llvm::LLVMConstInBoundsGEP(
+                    llvm::LLVMRustConstInBoundsGEP2(
+                        self.type_i8(),
                         self.const_bitcast(base_addr, self.type_i8p_ext(base_addr_space)),
                         &self.const_usize(offset.bytes()),
                         1,
@@ -303,7 +304,8 @@ impl ConstMethods<'tcx> for CodegenCx<'ll, 'tcx> {
             let base_addr = self.static_addr_of(init, alloc.align, None);
 
             let llval = unsafe {
-                llvm::LLVMConstInBoundsGEP(
+                llvm::LLVMRustConstInBoundsGEP2(
+                    self.type_i8(),
                     self.const_bitcast(base_addr, self.type_i8p()),
                     &self.const_usize(offset.bytes()),
                     1,

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -1011,7 +1011,8 @@ extern "C" {
     pub fn LLVMConstVector(ScalarConstantVals: *const &Value, Size: c_uint) -> &Value;
 
     // Constant expressions
-    pub fn LLVMConstInBoundsGEP(
+    pub fn LLVMRustConstInBoundsGEP2(
+        ty: &'a Type,
         ConstantVal: &'a Value,
         ConstantIndices: *const &'a Value,
         NumIndices: c_uint,

compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp

@@ -1551,6 +1551,16 @@ extern "C" void LLVMRustSetLinkage(LLVMValueRef V,
   LLVMSetLinkage(V, fromRust(RustLinkage));
 }
 
+extern "C" LLVMValueRef LLVMRustConstInBoundsGEP2(LLVMTypeRef Ty,
+                                                  LLVMValueRef ConstantVal,
+                                                  LLVMValueRef *ConstantIndices,
+                                                  unsigned NumIndices) {
+  ArrayRef<Constant *> IdxList(unwrap<Constant>(ConstantIndices, NumIndices),
+                               NumIndices);
+  Constant *Val = unwrap<Constant>(ConstantVal);
+  return wrap(ConstantExpr::getInBoundsGetElementPtr(unwrap(Ty), Val, IdxList));
+}
+
 // Returns true if both high and low were successfully set. Fails in case constant wasn’t any of
 // the common sizes (1, 8, 16, 32, 64, 128 bits)
 extern "C" bool LLVMRustConstInt128Get(LLVMValueRef CV, bool sext, uint64_t *high, uint64_t *low)