mirror/PS2Recomp
1
0
Fork 0
mirror of https://github.com/ran-j/PS2Recomp.git synced 2026-09-29 01:47:44 -04:00
Code Issues Packages Projects Releases Wiki Activity

Compare all 64 bits in the relational branches

Browse Source 
BEQ and BNE already compare the full GPR, but BLEZ, BGTZ, BLTZ and BGEZ (and
their likely/and-link variants) were emitted against the low word only. The
R5900 compares the whole 64-bit register, so any value whose upper half is
significant takes the wrong branch.

Compilers reach these opcodes through the dsll32/dsra32 sign-extension idiom,
which leaves a canonical value and hides the bug; code that keeps a genuine
64-bit quantity in the register does not.
This commit is contained in:
Sinan KARAKAYA
2026-08-17 18:29:01 +02:00
parent 5c906ddf4b
commit 20848417af
1 changed files with 8 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files
ps2xRecomp/src/lib/control_flow_emitter.cpp
+8 -4
View File
@@ -404,12 +404,16 @@ namespace ps2recomp
case OPCODE_BNE:
case OPCODE_BNEL:
return fmt::format("GPR_U64(ctx, {}) != GPR_U64(ctx, {})", rsReg, rtReg);
// The R5900 compares the full 64-bit GPR for the relational branches, as it
// already does for BEQ/BNE above. Comparing only the low word takes the wrong
// branch whenever the upper half is significant, which happens with the
// dsll32/dsra32 sign-extension idiom compilers emit ahead of these opcodes.
case OPCODE_BLEZ:
case OPCODE_BLEZL:
return fmt::format("GPR_S32(ctx, {}) <= 0", rsReg);
return fmt::format("GPR_S64(ctx, {}) <= 0", rsReg);
case OPCODE_BGTZ:
case OPCODE_BGTZL:
return fmt::format("GPR_S32(ctx, {}) > 0", rsReg);
return fmt::format("GPR_S64(ctx, {}) > 0", rsReg);
case OPCODE_REGIMM:
switch (m_branchInst.rt)
{
@@ -417,12 +421,12 @@ namespace ps2recomp
case REGIMM_BLTZL:
case REGIMM_BLTZAL:
case REGIMM_BLTZALL:
return fmt::format("GPR_S32(ctx, {}) < 0", rsReg);
return fmt::format("GPR_S64(ctx, {}) < 0", rsReg);
case REGIMM_BGEZ:
case REGIMM_BGEZL:
case REGIMM_BGEZAL:
case REGIMM_BGEZALL:
return fmt::format("GPR_S32(ctx, {}) >= 0", rsReg);
return fmt::format("GPR_S64(ctx, {}) >= 0", rsReg);
default:
return "false";
}