[llvm] [RISCV] Align stack size down to a multiple of 16 before using cm.push/pop. (PR #86073)

[Wang Pengcheng via llvm-commits]

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@@ -776,8 +778,10 @@ void RISCVFrameLowering::emitEpilogue(MachineFunction &MF,
   if (RVFI->isPushable(MF) && MBBI != MBB.end() &&
       MBBI->getOpcode() == RISCV::CM_POP) {
     // Use available stack adjustment in pop instruction to deallocate stack
-    // space.
-    uint64_t Spimm = std::min(StackSize, (uint64_t)48);
+    // space. Align the stack size down to a multiple of 16. This is needed for
+    // RVE.
+    // FIXME: Can we increase the stack size to a multiple of 16 insead?
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wangpc-pp wrote:

ditto.

https://github.com/llvm/llvm-project/pull/86073