aco: ignore blocked registers when checking edges in get_reg_impl()

If the only two registers available are consecutive and used by killed
operands, both of them will be blocked and fail the edge check.

Totals from 903 (0.66% of 135946) affected shaders:
VGPRs: 30892 -> 30884 (-0.03%)
CodeSize: 1584468 -> 1584044 (-0.03%); split: -0.05%, +0.02%
MaxWaves: 14374 -> 14378 (+0.03%)
Instrs: 306482 -> 306399 (-0.03%); split: -0.06%, +0.03%

Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>
Reviewed-by: Daniel Schürmann <daniel@schuermann.dev>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5626>

diff --git a/src/amd/compiler/aco_register_allocation.cpp b/src/amd/compiler/aco_register_allocation.cpp
index 9af9bdfe235f0cb09432f06a2b4aba93b00b10fd..a59a9af7add64501e06bbd023a1c7888f080d674 100644 (file)
--- a/src/amd/compiler/aco_register_allocation.cpp
+++ b/src/amd/compiler/aco_register_allocation.cpp
@@ -185,6 +185,13 @@ public:
       return false;
    }
 
+   bool is_empty_or_blocked(PhysReg start) {
+      if (regs[start] == 0xF0000000) {
+         return subdword_regs[start][start.byte()] + 1 <= 1;
+      }
+      return regs[start] + 1 <= 1;
+   }
+
    void clear(PhysReg start, RegClass rc) {
       if (rc.is_subdword())
          fill_subdword(start, rc.bytes(), 0);
@@ -947,9 +954,11 @@ std::pair<PhysReg, bool> get_reg_impl(ra_ctx& ctx,
    unsigned reg_hi = lb + size - 1;
    for (reg_lo = lb, reg_hi = lb + size - 1; reg_hi < ub; reg_lo += stride, reg_hi += stride) {
       /* first check the edges: this is what we have to fix to allow for num_moves > size */
-      if (reg_lo > lb && reg_file[reg_lo] != 0 && reg_file.get_id(PhysReg(reg_lo)) == reg_file.get_id(PhysReg(reg_lo).advance(-1)))
+      if (reg_lo > lb && !reg_file.is_empty_or_blocked(PhysReg(reg_lo)) &&
+          reg_file.get_id(PhysReg(reg_lo)) == reg_file.get_id(PhysReg(reg_lo).advance(-1)))
          continue;
-      if (reg_hi < ub - 1 && reg_file[reg_hi] != 0 && reg_file.get_id(PhysReg(reg_hi).advance(3)) == reg_file.get_id(PhysReg(reg_hi).advance(4)))
+      if (reg_hi < ub - 1 && !reg_file.is_empty_or_blocked(PhysReg(reg_hi).advance(3)) &&
+          reg_file.get_id(PhysReg(reg_hi).advance(3)) == reg_file.get_id(PhysReg(reg_hi).advance(4)))
          continue;
 
       /* second, check that we have at most k=num_moves elements in the window