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std.start: fix _start for mipsn32

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This is more similar to O32 than N64.
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Alex Rønne Petersen 2025-10-18 12:11:27 +02:00
parent adcfdce6be
commit 2305527342
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1 changed files with 40 additions and 21 deletions
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lib/std/start.zig
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@ -343,27 +343,46 @@ fn _start() callconv(.naked) noreturn {
\\ subu $sp, $sp, 16
\\ jalr $t9
,
.mips64, .mips64el =>
\\ move $fp, $zero
// This is needed because early MIPS versions don't support misaligned loads. Without
// this directive, the hidden `nop` inserted to fill the delay slot after `bal` would
// cause the two doublewords to be aligned to 4 bytes instead of 8.
\\ .balign 8
\\ bal 1f
\\ .gpdword .
\\ .gpdword %[posixCallMainAndExit]
\\1:
// The `gp` register on MIPS serves a similar purpose to `r2` (ToC pointer) on PPC64.
\\ ld $gp, 0($ra)
\\ dsubu $gp, $ra, $gp
\\ ld $t9, 8($ra)
\\ daddu $t9, $t9, $gp
\\ move $ra, $zero
\\ move $a0, $sp
\\ and $sp, -16
\\ dsubu $sp, $sp, 16
\\ jalr $t9
,
.mips64, .mips64el => switch (builtin.abi) {
.gnuabin32, .muslabin32 =>
\\ move $fp, $zero
\\ bal 1f
\\ .gpword .
\\ .gpword %[posixCallMainAndExit]
\\1:
// The `gp` register on MIPS serves a similar purpose to `r2` (ToC pointer) on PPC64.
\\ lw $gp, 0($ra)
\\ subu $gp, $ra, $gp
\\ lw $t9, 4($ra)
\\ addu $t9, $t9, $gp
\\ move $ra, $zero
\\ move $a0, $sp
\\ and $sp, -8
\\ subu $sp, $sp, 16
\\ jalr $t9
,
else =>
\\ move $fp, $zero
// This is needed because early MIPS versions don't support misaligned loads. Without
// this directive, the hidden `nop` inserted to fill the delay slot after `bal` would
// cause the two doublewords to be aligned to 4 bytes instead of 8.
\\ .balign 8
\\ bal 1f
\\ .gpdword .
\\ .gpdword %[posixCallMainAndExit]
\\1:
// The `gp` register on MIPS serves a similar purpose to `r2` (ToC pointer) on PPC64.
\\ ld $gp, 0($ra)
\\ dsubu $gp, $ra, $gp
\\ ld $t9, 8($ra)
\\ daddu $t9, $t9, $gp
\\ move $ra, $zero
\\ move $a0, $sp
\\ and $sp, -16
\\ dsubu $sp, $sp, 16
\\ jalr $t9
,
},
.powerpc, .powerpcle =>
// Set up the initial stack frame, and clear the back chain pointer.
// r1 = SP, r31 = FP