[llvm] d7ffa82 - [RISCV] Improve 64-bit integer constant materialization for more cases.

[Craig Topper via llvm-commits]

Author: Craig Topper
Date: 2021-04-02T10:18:08-07:00
New Revision: d7ffa82a8e621ce9a19b98c922adc53d6b7cd9f3

URL: https://github.com/llvm/llvm-project/commit/d7ffa82a8e621ce9a19b98c922adc53d6b7cd9f3
DIFF: https://github.com/llvm/llvm-project/commit/d7ffa82a8e621ce9a19b98c922adc53d6b7cd9f3.diff

LOG: [RISCV] Improve 64-bit integer constant materialization for more cases.

For positive constants we try shifting left to remove leading zeros
and fill the bottom bits with 1s. We then materialize that constant
shift it right.

This patch adds a new strategy to try filling the bottom bits with
zeros instead. This catches some additional cases.

Added: 
    

Modified: 
    llvm/lib/Target/RISCV/MCTargetDesc/RISCVMatInt.cpp
    llvm/test/CodeGen/RISCV/calling-conv-half.ll
    llvm/test/CodeGen/RISCV/imm.ll
    llvm/test/MC/RISCV/rv64i-aliases-valid.s

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVMatInt.cpp b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVMatInt.cpp
index d9c719765abfb..72f7faf74576c 100644
--- a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVMatInt.cpp
+++ b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVMatInt.cpp
@@ -94,6 +94,16 @@ InstSeq generateInstSeq(int64_t Val, bool IsRV64) {
     generateInstSeqImpl(Val, IsRV64, TmpSeq);
     TmpSeq.push_back(RISCVMatInt::Inst(RISCV::SRLI, ShiftAmount));
 
+    // Keep the new sequence if it is an improvement.
+    if (TmpSeq.size() < Res.size())
+      Res = TmpSeq;
+
+    // Some cases can benefit from filling the lower bits with zeros instead.
+    Val &= maskTrailingZeros<uint64_t>(ShiftAmount);
+    TmpSeq.clear();
+    generateInstSeqImpl(Val, IsRV64, TmpSeq);
+    TmpSeq.push_back(RISCVMatInt::Inst(RISCV::SRLI, ShiftAmount));
+
     // Keep the new sequence if it is an improvement.
     if (TmpSeq.size() < Res.size())
       Res = TmpSeq;

diff  --git a/llvm/test/CodeGen/RISCV/calling-conv-half.ll b/llvm/test/CodeGen/RISCV/calling-conv-half.ll
index 46251f9660d4e..fec5d4bf70f82 100644
--- a/llvm/test/CodeGen/RISCV/calling-conv-half.ll
+++ b/llvm/test/CodeGen/RISCV/calling-conv-half.ll
@@ -347,10 +347,9 @@ define i32 @caller_half_on_stack() nounwind {
 ; RV64IF:       # %bb.0:
 ; RV64IF-NEXT:    addi sp, sp, -16
 ; RV64IF-NEXT:    sd ra, 8(sp) # 8-byte Folded Spill
-; RV64IF-NEXT:    lui a0, 256
-; RV64IF-NEXT:    addiw a0, a0, -11
-; RV64IF-NEXT:    slli a0, a0, 12
-; RV64IF-NEXT:    addi t0, a0, -1792
+; RV64IF-NEXT:    addi a0, zero, -183
+; RV64IF-NEXT:    slli a0, a0, 40
+; RV64IF-NEXT:    srli t0, a0, 32
 ; RV64IF-NEXT:    addi a0, zero, 1
 ; RV64IF-NEXT:    addi a1, zero, 2
 ; RV64IF-NEXT:    addi a2, zero, 3

diff  --git a/llvm/test/CodeGen/RISCV/imm.ll b/llvm/test/CodeGen/RISCV/imm.ll
index 2c9462d7cbbfc..f0af4ffe8c747 100644
--- a/llvm/test/CodeGen/RISCV/imm.ll
+++ b/llvm/test/CodeGen/RISCV/imm.ll
@@ -375,8 +375,7 @@ define i64 @imm_right_shifted_lui_1() nounwind {
 ;
 ; RV64I-LABEL: imm_right_shifted_lui_1:
 ; RV64I:       # %bb.0:
-; RV64I-NEXT:    lui a0, 983072
-; RV64I-NEXT:    addiw a0, a0, -1
+; RV64I-NEXT:    lui a0, 983056
 ; RV64I-NEXT:    srli a0, a0, 16
 ; RV64I-NEXT:    ret
   ret i64 281474976706561 ; 0xFFFF_FFFF_F001

diff  --git a/llvm/test/MC/RISCV/rv64i-aliases-valid.s b/llvm/test/MC/RISCV/rv64i-aliases-valid.s
index 7333b3187a271..a51a87b23c511 100644
--- a/llvm/test/MC/RISCV/rv64i-aliases-valid.s
+++ b/llvm/test/MC/RISCV/rv64i-aliases-valid.s
@@ -118,8 +118,7 @@ li x5, 0x100004000
 # CHECK-EXPAND-NEXT: addiw t1, t1, 1
 # CHECK-EXPAND-NEXT: slli t1, t1, 32
 li x6, 0x100100000000
-# CHECK-EXPAND: lui t2, 983072
-# CHECK-EXPAND-NEXT: addiw t2, t2, -1
+# CHECK-EXPAND: lui t2, 983056
 # CHECK-EXPAND-NEXT: srli t2, t2, 16
 li x7, 0xFFFFFFFFF001
 # CHECK-EXPAND: lui s0, 65536