[PowerPC] Handle CALL_RM like CALL for 32-bit ELF #72758
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✅ With the latest revision this PR passed the C/C++ code formatter. |
If a function call has the strictfp attribute, its opcode changes from CALL to CALL_RM. If the call uses the secure PLT for 32-bit ELF, then it must getGlobalBaseReg() to set r30.
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Handle CALL_RM like CALL for 32-bit ELF. If a function call has the strictfp attribute, its opcode changes from CALL to CALL_RM. If a call uses the secure PLT, then it must getGlobalBaseReg() to set r30. After I rebuilt xenocara/lib/pixman with this change, Xorg stopped crashing on my macppc. pixman uses cc -ftrapping-math which puts strictfp on each function call. llvm/llvm-project#72758 ok jca@ tobhe@ deraadt@
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| @@ -0,0 +1,21 @@ | |||
| ; RUN: llc < %s -mtriple=powerpc-unknown-linux-gnu -mattr=+secure-plt -relocation-model=pic | FileCheck %s | |||
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Can we use auto generate script for it?
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@kernigh Ping. |
| @@ -5475,7 +5475,8 @@ void PPCDAGToDAGISel::Select(SDNode *N) { | |||
| // generate secure plt code for TLS symbols. | |||
| getGlobalBaseReg(); | |||
| } break; | |||
| case PPCISD::CALL: { | |||
| case PPCISD::CALL: | |||
| case PPCISD::CALL_RM: { | |||
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Are your targeting this for SPE? SPE should have no floating point instructions? So round mode should not be a concern? For SPE, we may stop generate CALL_RM where it is generated. Note that CALL_RM performs worse than normal CALL even after instruction selection. They are selected to different instructions.
If for other PPC32 targets, the fix looks reasonable to me.
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Are your targeting this for SPE?
This is not for SPE.
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LGTM as long as @ecnelises's comment about the LIT case is addressed.
Handle CALL_RM like CALL for 32-bit ELF. If a function call has the strictfp attribute, its opcode changes from CALL to CALL_RM. If a call uses the secure PLT, then it must getGlobalBaseReg() to set r30. After I rebuilt xenocara/lib/pixman with this change, Xorg stopped crashing on my macppc. pixman uses cc -ftrapping-math which puts strictfp on each function call. llvm#72758 ok jca@ tobhe@ deraadt@
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It would be nice to get this in. |
Please let us know if need us to commit this pr. @kernigh |
He does, but there was the issue of the test case being updated. |
If a function call has the strictfp attribute, its opcode changes from CALL to CALL_RM. If the call uses the secure PLT for 32-bit ELF, then it must getGlobalBaseReg() to set r30.
This fixes a bug that I described in (OpenBSD) macppc clang-16 -ftrapping-math crashes Xorg. The short version is that clang -ftrapping-math broke code like
int main(void) { time(NULL); }by forgetting to set r30 before using the secure PLT.