Bug 305948

Summary: ppc64: code generation for ShlD64 / ShrD64 asserts
Product: [Developer tools] valgrind Reporter: Florian Krohm <flo2030>
Component: vexAssignee: Florian Krohm <flo2030>
Status: CLOSED FIXED    
Severity: normal CC: cel
Priority: NOR    
Version First Reported In: unspecified   
Target Milestone: ---   
Platform: unspecified   
OS: Linux   
Latest Commit: Version Fixed/Implemented In:
Sentry Crash Report:

Description Florian Krohm 2012-08-28 20:47:47 UTC 
Consider this IR:

STbe(0x4040070:I64) = ReinterpD64asI64(ShlD64(ReinterpI64asD64(LDbe:I64(0x40400C0:I64)),LDbe:I8(0x4040110:I64)))

as generated by the V-bit tester. When run through valgrind it will assert like so:
vex: priv/host_ppc_defs.c:3158 (mkFormZ22): Assertion `constant < 0x40' failed.

The reason is that in host_ppc_isel.c around line 3970 the shift amount for Iop_ShlD64 is compiled into a register or an immediate value (iselWordExpr_RI).
Then a PPCInstr_DfpShift insn is created.
When code is later generated for Pin_DfpShift (host_ppc_defs.c line 2460)
it is assumed that the shift amount is an immediate value:

shift =  i->Pin.DfpShift.shift->Pri.Imm;

And because that's not  the case when compiling the above IR we will run into an assert in mkFormZ22.
Comment 1 Florian Krohm 2012-08-28 23:29:21 UTC 
Above analysis also applies to ShlD128 / ShrD128. Those ops have the same problem.
Comment 2 Julian Seward 2012-08-29 06:47:51 UTC 
Florian, nice catch.  Does the 32 bit ppc insn selection also fail?
Comment 3 Florian Krohm 2012-09-01 17:07:27 UTC 
The shift amount for the ppc DFP shift insn is given in an immediate field.  Therefore, the insn selector cannot find a cover for the IR in comment #1.
The vbit-tester needs to be adjusted to deal with this.
I'm leaving this bug open and assign it to myself.
Comment 4 Carl Love 2012-09-04 22:38:16 UTC 
Added vassert for DFP shift value to make sure shift value is an immediate value. Change made to file VEX/priv/host_ppc_isel.c

VEX committed revision 2512
Comment 5 Florian Krohm 2012-09-13 19:42:06 UTC 
Fixed in VEX r2529 and valgrind r12969.
Testing of Iop_ShlD64 etc is now enabled for the vbit tester on ppc platforms.
Comment 6 Carl Love 2024-06-24 15:33:28 UTC 
The issue was fixed.  No additional issues have been found related to this bug.  Closing.