[llvm] [RISCV] Separate doLocalPostpass into new pass and move to post vector regalloc (PR #88295)

[Philip Reames via llvm-commits]

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@@ -288,32 +288,44 @@ define <vscale x 16 x i64> @vector_interleave_nxv16i64_nxv8i64(<vscale x 8 x i64
 ; CHECK-NEXT:    addi sp, sp, -16
 ; CHECK-NEXT:    .cfi_def_cfa_offset 16
 ; CHECK-NEXT:    csrr a0, vlenb
-; CHECK-NEXT:    slli a0, a0, 3
+; CHECK-NEXT:    slli a0, a0, 4
 ; CHECK-NEXT:    sub sp, sp, a0
-; CHECK-NEXT:    .cfi_escape 0x0f, 0x0d, 0x72, 0x00, 0x11, 0x10, 0x22, 0x11, 0x08, 0x92, 0xa2, 0x38, 0x00, 0x1e, 0x22 # sp + 16 + 8 * vlenb
-; CHECK-NEXT:    vmv8r.v v0, v8
+; CHECK-NEXT:    .cfi_escape 0x0f, 0x0d, 0x72, 0x00, 0x11, 0x10, 0x22, 0x11, 0x10, 0x92, 0xa2, 0x38, 0x00, 0x1e, 0x22 # sp + 16 + 16 * vlenb
+; CHECK-NEXT:    csrr a0, vlenb
+; CHECK-NEXT:    slli a0, a0, 3
+; CHECK-NEXT:    add a0, sp, a0
+; CHECK-NEXT:    addi a0, a0, 16
+; CHECK-NEXT:    vs8r.v v8, (a0) # Unknown-size Folded Spill
 ; CHECK-NEXT:    csrr a0, vlenb
 ; CHECK-NEXT:    srli a0, a0, 1
 ; CHECK-NEXT:    vsetvli a1, zero, e16, m2, ta, mu
 ; CHECK-NEXT:    vid.v v24
-; CHECK-NEXT:    vand.vi v26, v24, 1
-; CHECK-NEXT:    vmsne.vi v10, v26, 0
-; CHECK-NEXT:    vsrl.vi v8, v24, 1
-; CHECK-NEXT:    vmv8r.v v24, v0
-; CHECK-NEXT:    vmv4r.v v12, v4
-; CHECK-NEXT:    vmv1r.v v0, v10
-; CHECK-NEXT:    vadd.vx v8, v8, a0, v0.t
+; CHECK-NEXT:    vsrl.vi v6, v24, 1
+; CHECK-NEXT:    vand.vi v8, v24, 1
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preames wrote:

There's something a bit odd here with both the before and after code.  This vand.vi appears to be the last use of the v24 register.  Why are we using v8 as a temporary here at all?  I don't believe vand.vi has a register overlap constraint...  If we reused v24 here, we'd reduce register pressure slightly. 

https://github.com/llvm/llvm-project/pull/88295