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fix(barrel_shifter): should not modify cpsr when amount == 0

This commit is contained in:
Rekai Nyangadzayi Musuka 2022-01-18 13:30:41 -04:00
parent a7a44c4463
commit 25c57a4cc7
1 changed files with 6 additions and 6 deletions
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12
src/cpu/arm/barrel_shifter.zig
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@ -81,7 +81,7 @@ pub fn logicalLeft(comptime S: bool, cpsr: *CPSR, rm: u32, total_amount: u8) u32
// We can perform a well-defined shift here // We can perform a well-defined shift here
result = rm << amount; result = rm << amount;
if (S) { if (S and total_amount != 0) {
const carry_bit = @truncate(u5, bit_count - amount); const carry_bit = @truncate(u5, bit_count - amount);
cpsr.c.write(rm >> carry_bit & 1 == 1); cpsr.c.write(rm >> carry_bit & 1 == 1);
} }
@ -107,7 +107,7 @@ pub fn logicalRight(comptime S: bool, cpsr: *CPSR, rm: u32, total_amount: u32) u
if (total_amount < bit_count) { if (total_amount < bit_count) {
// We can perform a well-defined shift // We can perform a well-defined shift
result = rm >> amount; result = rm >> amount;
if (S) cpsr.c.write(rm >> (amount - 1) & 1 == 1); if (S and total_amount != 0) cpsr.c.write(rm >> (amount - 1) & 1 == 1);
} else { } else {
if (S) { if (S) {
if (total_amount == bit_count) { if (total_amount == bit_count) {
@ -130,7 +130,7 @@ pub fn arithmeticRight(comptime S: bool, cpsr: *CPSR, rm: u32, total_amount: u8)
var result: u32 = 0x0000_0000; var result: u32 = 0x0000_0000;
if (total_amount < bit_count) { if (total_amount < bit_count) {
result = @bitCast(u32, @bitCast(i32, rm) >> amount); result = @bitCast(u32, @bitCast(i32, rm) >> amount);
if (S) cpsr.c.write(rm >> (amount - 1) & 1 == 1); if (S and total_amount != 0) cpsr.c.write(rm >> (amount - 1) & 1 == 1);
} else { } else {
if (S) { if (S) {
// ASR #32 and ASR #>32 have the same result // ASR #32 and ASR #>32 have the same result
@ -142,10 +142,10 @@ pub fn arithmeticRight(comptime S: bool, cpsr: *CPSR, rm: u32, total_amount: u8)
std.debug.panic("[BarrelShifter] implement arithmetic shift right", .{}); std.debug.panic("[BarrelShifter] implement arithmetic shift right", .{});
} }
pub fn rotateRight(comptime S: bool, cpsr: *CPSR, rm: u32, amount: u8) u32 { pub fn rotateRight(comptime S: bool, cpsr: *CPSR, rm: u32, total_amount: u8) u32 {
const result = std.math.rotr(u32, rm, amount); const result = std.math.rotr(u32, rm, total_amount);
if (S and result != 0) { if (S and total_amount != 0) {
cpsr.c.write(result >> 31 & 1 == 1); cpsr.c.write(result >> 31 & 1 == 1);
} }