Messages in this thread |  | | Date | Tue, 5 May 2026 10:56:58 -0500 | | From | Segher Boessenkool <> | | Subject | Re: [PATCH v1 1/6] objtool/powerpc: Add build-time fixup of alternate feature branch targets |
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Hi!
On Tue, May 05, 2026 at 04:45:39PM +0200, Peter Zijlstra wrote: > On Tue, May 05, 2026 at 02:16:23PM +0530, Sathvika Vasireddy wrote: > > switch (opcode) { > > + case 16: > > Like case 18 below, this wants a comment describing which instruction > this is; bclr ?
Yes. It is 19/16, b[c]lr (primary opcode 19, secondary opcode 16).
Where is it described what INSN_RETURN actually means for objtool? Not in the header file :-(
For PowerPC, all three of b[c]lr[l], b[c]ctr[l], and b[c]tar[l] are indirect jumps, to an address in a register. They do absolutely nothing typically done in a function epilog, like "return" insns in some other archs do. But the BH field ("branch hint") in the instruction helps predict the control flow involving the insn as something in a call and return pattern :-)
Segher
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