Merge pull request rust-lang#37 from reitermarkus/call-abi

Refactor call ABI according to LLVM version.

Author: MabezDev

src/librustc_target/abi/call/xtensa.rs

@@ -1,102 +1,98 @@
-// reference: https://github.com/espressif/clang-xtensa/commit/6fb488d2553f06029e6611cf81c6efbd45b56e47#diff-aa74ae1e1ab6b7149789237edb78e688R8450
+// reference: https://github.com/MabezDev/llvm-project/blob/xtensa_release_9.0.1_with_rust_patches-31-05-2020-cherry-pick/clang/lib/CodeGen/TargetInfo.cpp#L9668-L9767
 
 use crate::abi::call::{ArgAbi, FnAbi, Reg, Uniform};
+use crate::abi::{Abi, Size};
 
-const NUM_ARG_GPR: u64 = 6;
+const NUM_ARG_GPRS: u64 = 6;
 const MAX_ARG_IN_REGS_SIZE: u64 = 4 * 32;
-// const MAX_ARG_DIRECT_SIZE: u64 = MAX_ARG_IN_REGS_SIZE;
 const MAX_RET_IN_REGS_SIZE: u64 = 2 * 32;
 
 fn classify_ret_ty<Ty>(arg: &mut ArgAbi<'_, Ty>, xlen: u64) {
-    // The rules for return and argument types are the same, so defer to
-    // classifyArgumentType.
-    classify_arg_ty(arg, xlen, &mut 2); // two as max return size
+    if arg.is_ignore() {
+        return;
+    }
+
+    // The rules for return and argument types are the same,
+    // so defer to `classify_arg_ty`.
+    let mut arg_gprs_left = 2;
+    let fixed = true;
+    classify_arg_ty(arg, xlen, fixed, &mut arg_gprs_left);
 }
 
-fn classify_arg_ty<Ty>(arg: &mut ArgAbi<'_, Ty>, xlen: u64, remaining_gpr: &mut u64) {
-    // Determine the number of GPRs needed to pass the current argument
-    // according to the ABI. 2*XLen-aligned varargs are passed in "aligned"
-    // register pairs, so may consume 3 registers.
+fn classify_arg_ty<Ty>(arg: &mut ArgAbi<'_, Ty>, xlen: u64, fixed: bool, arg_gprs_left: &mut u64) {
+    assert!(*arg_gprs_left <= NUM_ARG_GPRS, "Arg GPR tracking underflow");
 
-    let arg_size = arg.layout.size;
-    if arg_size.bits() > MAX_ARG_IN_REGS_SIZE {
-        arg.make_indirect();
+    // Ignore empty structs/unions.
+    if arg.layout.is_zst() {
         return;
     }
 
-    let alignment = arg.layout.align.abi;
-    let mut required_gpr = 1u64; // at least one per arg
+    let size = arg.layout.size.bits();
+    let needed_align = arg.layout.align.abi.bits();
+    let mut must_use_stack = false;
+
+    // Determine the number of GPRs needed to pass the current argument
+    // according to the ABI. 2*XLen-aligned varargs are passed in "aligned"
+    // register pairs, so may consume 3 registers.
+    let mut needed_arg_gprs = 1u64;
 
-    if alignment.bits() == 2 * xlen {
-        required_gpr = 2 + (*remaining_gpr % 2);
-    } else if arg_size.bits() > xlen && arg_size.bits() <= MAX_ARG_IN_REGS_SIZE {
-        required_gpr = (arg_size.bits() + (xlen - 1)) / xlen;
+    if !fixed && needed_align == 2 * xlen {
+        needed_arg_gprs = 2 + (*arg_gprs_left % 2);
+    } else if size > xlen && size <= MAX_ARG_IN_REGS_SIZE {
+        needed_arg_gprs = (size + xlen - 1) / xlen;
     }
 
-    let mut stack_required = false;
-    if required_gpr > *remaining_gpr {
-        stack_required = true;
-        required_gpr = *remaining_gpr;
+    if needed_arg_gprs > *arg_gprs_left {
+        must_use_stack = true;
+        needed_arg_gprs = *arg_gprs_left;
     }
-    *remaining_gpr -= required_gpr;
+    *arg_gprs_left -= needed_arg_gprs;
 
-    // if  a value can fit in a reg and the
-    // stack is not required, extend
-    if !arg.layout.is_aggregate() {
-        // non-aggregate types
-        if arg_size.bits() < xlen && !stack_required {
+    if !arg.layout.is_aggregate() && !matches!(arg.layout.abi, Abi::Vector { .. }) {
+        // All integral types are promoted to `xlen`
+        // width, unless passed on the stack.
+        if size < xlen && !must_use_stack {
             arg.extend_integer_width_to(xlen);
+            return;
         }
-    } else if arg_size.bits() as u64 <= MAX_ARG_IN_REGS_SIZE {
-        // aggregate types
-        // Aggregates which are <= 4*32 will be passed in registers if possible,
-        // so coerce to integers.
 
-        // Use a single XLen int if possible, 2*XLen if 2*XLen alignment is
-        // required, and a 2-element XLen array if only XLen alignment is
+        return;
+    }
+
+    // Aggregates which are <= 4 * 32 will be passed in
+    // registers if possible, so coerce to integers.
+    if size as u64 <= MAX_ARG_IN_REGS_SIZE {
+        let alignment = arg.layout.align.abi.bits();
+
+        // Use a single `xlen` int if possible, 2 * `xlen` if 2 * `xlen` alignment
+        // is required, and a 2-element `xlen` array if only `xlen` alignment is
         // required.
-        // if alignment == 2 * xlen {
-        //     arg.extend_integer_width_to(xlen * 2);
-        // } else {
-        //     arg.extend_integer_width_to(arg_size + (xlen - 1) / xlen);
-        // }
-        if alignment.bits() == 2 * xlen {
-            arg.cast_to(Uniform { unit: Reg::i64(), total: arg_size });
+        if size <= xlen {
+            arg.cast_to(Reg::i32());
+            return;
+        } else if alignment == 2 * xlen {
+            arg.cast_to(Reg::i64());
+            return;
         } else {
-            //FIXME array type - this should be a homogenous array type
-            // arg.extend_integer_width_to(arg_size + (xlen - 1) / xlen);
+            let total = Size::from_bits(((size + xlen - 1) / xlen) * xlen);
+            arg.cast_to(Uniform { unit: Reg::i32(), total });
+            return;
         }
-    } else {
-        // if we get here the stack is required
-        assert!(stack_required);
-        arg.make_indirect();
     }
 
-    // if arg_size as u64 <= MAX_ARG_IN_REGS_SIZE {
-    //     let align = arg.layout.align.abi.bytes();
-    //     let total = arg.layout.size;
-    //     arg.cast_to(Uniform {
-    //         unit: if align <= 4 { Reg::i32() } else { Reg::i64() },
-    //         total
-    //     });
-    //     return;
-    // }
+    arg.make_indirect();
 }
 
-pub fn compute_abi_info<Ty>(fabi: &mut FnAbi<'_, Ty>, xlen: u64) {
-    if !fabi.ret.is_ignore() {
-        classify_ret_ty(&mut fabi.ret, xlen);
-    }
+pub fn compute_abi_info<Ty>(fn_abi: &mut FnAbi<'_, Ty>, xlen: u64) {
+    classify_ret_ty(&mut fn_abi.ret, xlen);
 
-    let return_indirect =
-        fabi.ret.layout.size.bits() > MAX_RET_IN_REGS_SIZE || fabi.ret.is_indirect();
+    let is_ret_indirect =
+        fn_abi.ret.is_indirect() || fn_abi.ret.layout.size.bits() > MAX_RET_IN_REGS_SIZE;
 
-    let mut remaining_gpr = if return_indirect { NUM_ARG_GPR - 1 } else { NUM_ARG_GPR };
+    let mut arg_gprs_left = if is_ret_indirect { NUM_ARG_GPRS - 1 } else { NUM_ARG_GPRS };
 
-    for arg in &mut fabi.args {
-        if arg.is_ignore() {
-            continue;
-        }
-        classify_arg_ty(arg, xlen, &mut remaining_gpr);
+    for arg in &mut fn_abi.args {
+        let fixed = true;
+        classify_arg_ty(arg, xlen, fixed, &mut arg_gprs_left);
     }
 }