[llvm] [RISCV] Add another packh+packw pattern. (PR #152744)

[Craig Topper via llvm-commits]

https://github.com/topperc created https://github.com/llvm/llvm-project/pull/152744

If the upper 32 bits are demanded, we might have a sext_inreg in
the pattern on the byte shifted by 24. We can also match this case
since packw sign extends from bit 31.

>From fb8f9d66249aefe4fe0b302b298175f2f9bb0aaa Mon Sep 17 00:00:00 2001
From: Craig Topper <craig.topper at sifive.com>
Date: Fri, 8 Aug 2025 07:52:23 -0700
Subject: [PATCH 1/2] Pre-commit test.

---
 llvm/test/CodeGen/RISCV/rv64zbkb.ll | 32 +++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/llvm/test/CodeGen/RISCV/rv64zbkb.ll b/llvm/test/CodeGen/RISCV/rv64zbkb.ll
index f2c41db781067..56dedbd7aa0c3 100644
--- a/llvm/test/CodeGen/RISCV/rv64zbkb.ll
+++ b/llvm/test/CodeGen/RISCV/rv64zbkb.ll
@@ -495,6 +495,38 @@ define void @pack_lo_packh_hi_packh_3(i8 %0, i8 %1, i8 %2, i8 %3, ptr %p) nounwi
   ret void
 }
 
+define i32 @pack_lo_packh_hi_packh_4(i8 zeroext %0, i8 zeroext %1, i8 zeroext %2, i8 zeroext %3, ptr %p) nounwind {
+; RV64I-LABEL: pack_lo_packh_hi_packh_4:
+; RV64I:       # %bb.0:
+; RV64I-NEXT:    slli a1, a1, 8
+; RV64I-NEXT:    slli a2, a2, 16
+; RV64I-NEXT:    slliw a3, a3, 24
+; RV64I-NEXT:    or a0, a0, a1
+; RV64I-NEXT:    or a2, a2, a3
+; RV64I-NEXT:    or a0, a0, a2
+; RV64I-NEXT:    ret
+;
+; RV64ZBKB-LABEL: pack_lo_packh_hi_packh_4:
+; RV64ZBKB:       # %bb.0:
+; RV64ZBKB-NEXT:    slli a2, a2, 16
+; RV64ZBKB-NEXT:    slliw a3, a3, 24
+; RV64ZBKB-NEXT:    packh a0, a0, a1
+; RV64ZBKB-NEXT:    or a0, a0, a2
+; RV64ZBKB-NEXT:    or a0, a0, a3
+; RV64ZBKB-NEXT:    ret
+  %a = zext i8 %0 to i32
+  %b = zext i8 %1 to i32
+  %c = zext i8 %2 to i32
+  %d = zext i8 %3 to i32
+  %e = shl i32 %b, 8
+  %f = shl i32 %c, 16
+  %g = shl i32 %d, 24
+  %h = or i32 %a, %e
+  %i = or i32 %h, %f
+  %j = or i32 %i, %g
+  ret i32 %j
+}
+
 define void @pack_lo_zext_hi_packh(i16 zeroext %0, i8 zeroext %1, i8 zeroext %2, ptr %p) nounwind {
 ; RV64I-LABEL: pack_lo_zext_hi_packh:
 ; RV64I:       # %bb.0:

>From 0d8144c0b2d1b86612efccbdca314ce950bdee69 Mon Sep 17 00:00:00 2001
From: Craig Topper <craig.topper at sifive.com>
Date: Fri, 8 Aug 2025 08:13:45 -0700
Subject: [PATCH 2/2] [RISCV] Add another packh+packw pattern.

If the upper 32 bits are demanded, we might have a sext_inreg in
the pattern on the byte shifted by 24. We can also match this case
since packw sign extends from bit 31.
---
 llvm/lib/Target/RISCV/RISCVInstrInfoZb.td | 5 +++++
 llvm/test/CodeGen/RISCV/rv64zbkb.ll       | 6 ++----
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/llvm/lib/Target/RISCV/RISCVInstrInfoZb.td b/llvm/lib/Target/RISCV/RISCVInstrInfoZb.td
index 413ad8b2f9cc9..ee623d3ad5e04 100644
--- a/llvm/lib/Target/RISCV/RISCVInstrInfoZb.td
+++ b/llvm/lib/Target/RISCV/RISCVInstrInfoZb.td
@@ -692,6 +692,11 @@ def : Pat<(binop_allwusers<or>
                    (shl GPR:$op1rs1, (XLenVT 24))),
                (shl (zexti8 (XLenVT GPR:$op1rs2)), (XLenVT 16))),
           (PACKW GPR:$rs1, (XLenVT (PACKH GPR:$op1rs1, GPR:$op1rs2)))>;
+
+def : Pat<(i64 (or (or (zexti16 (XLenVT GPR:$rs1)),
+                       (shl (zexti8 (XLenVT GPR:$op1rs2)), (XLenVT 16))),
+                   (sext_inreg (shl GPR:$op1rs1, (XLenVT 24)), i32))),
+          (PACKW GPR:$rs1, (XLenVT (PACKH GPR:$op1rs1, GPR:$op1rs2)))>;
 } // Predicates = [HasStdExtZbkb, IsRV64]
 
 let Predicates = [HasStdExtZbb, IsRV32] in
diff --git a/llvm/test/CodeGen/RISCV/rv64zbkb.ll b/llvm/test/CodeGen/RISCV/rv64zbkb.ll
index 56dedbd7aa0c3..4537d187a9857 100644
--- a/llvm/test/CodeGen/RISCV/rv64zbkb.ll
+++ b/llvm/test/CodeGen/RISCV/rv64zbkb.ll
@@ -508,11 +508,9 @@ define i32 @pack_lo_packh_hi_packh_4(i8 zeroext %0, i8 zeroext %1, i8 zeroext %2
 ;
 ; RV64ZBKB-LABEL: pack_lo_packh_hi_packh_4:
 ; RV64ZBKB:       # %bb.0:
-; RV64ZBKB-NEXT:    slli a2, a2, 16
-; RV64ZBKB-NEXT:    slliw a3, a3, 24
 ; RV64ZBKB-NEXT:    packh a0, a0, a1
-; RV64ZBKB-NEXT:    or a0, a0, a2
-; RV64ZBKB-NEXT:    or a0, a0, a3
+; RV64ZBKB-NEXT:    packh a1, a3, a2
+; RV64ZBKB-NEXT:    packw a0, a0, a1
 ; RV64ZBKB-NEXT:    ret
   %a = zext i8 %0 to i32
   %b = zext i8 %1 to i32