[llvm-dev] Expanding SDNodes (original) (raw)

Liad Mordekoviz via llvm-dev llvm-dev at lists.llvm.org
Mon Nov 20 03:31:01 PST 2017

Hello all,

I’ve been working on writing a backend, I was testing zext, and during the first run of combining llc does the following thing:

=== zext Creating new node: t3: i16 = truncate t2 Creating new node: t5: ch = CopyToReg t0, Register:i32 %vreg1, t2 Creating new node: t6: i32 = zeroextend t3 Creating new node: t9: ch = MyArchISD::RETFLAG t8, Register:i32 %R0, t8:1 Initial selection DAG: BB#0 'zext:entry' SelectionDAG has 10 nodes: t0: ch = EntryToken t2: i32,ch = CopyFromReg t0, Register:i32 %vreg0 t5: ch = CopyToReg t0, Register:i32 %vreg1, t2 t3: i16 = truncate t2 t6: i32 = zeroextend t3 t8: ch,glue = CopyToReg t5, Register:i32 %R0, t6 t9: ch =MyArchISD::RETFLAG t8, Register:i32 %R0, t8:1

Combining: t9: ch =MyArchISD::RETFLAG t8, Register:i32 %R0, t8:1 Combining: t8: ch,glue = CopyToReg t5, Register:i32 %R0, t6 Combining: t7: i32 = Register %R0 Combining: t6: i32 = zeroextend t3 Creating constant: t10: i32 = Constant<65535> Creating new node: t11: i32 = and t2, Constant:i32<65535> ... into: t11: i32 = and t2, Constant:i32<65535>

I was wondering if there is a way to expand the t6 node to “zext t3” so it won’t combine? (Maybe defining some pattern on my backend’s tablegen or something like that) Thanks, Liad. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20171120/0561142a/attachment.html>

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