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https://github.com/c64scene-ar/llvm-6502.git
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9379557478
This patch just uses a peephole test for "add; compare; branch" sequences within a single block. The IR optimizers already convert loops to decrement-and-branch-on-nonzero form in some cases, so even this simplistic test triggers many times during a clang bootstrap and projects/test-suite run. It looks like there are still cases where we need to more strongly prefer branches on nonzero though. E.g. I saw a case where a loop that started out with a check for 0 ended up with a check for -1. I'll try to look at that sometime. I ended up adding the Reference class because MachineInstr::readsRegister() doesn't check for subregisters (by design, as far as I could tell). git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@187723 91177308-0d34-0410-b5e6-96231b3b80d8
70 lines
2.0 KiB
Python
70 lines
2.0 KiB
Python
# Test 64-bit BRANCH RELATIVE ON COUNT in cases where some branches are out
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# of range.
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# RUN: python %s | llc -mtriple=s390x-linux-gnu | FileCheck %s
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# Construct:
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#
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# loopN:
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# load of countN
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# ...
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# loop0:
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# 0xffd8 bytes, from MVIY instructions
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# conditional branch to main
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# after0:
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# ...
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# decrement of countN
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# conditional branch to loopN
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# afterN:
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#
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# Each load occupies 6 bytes. Each decrement and branch occupies 4
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# bytes if BRCTG can be used, otherwise it occupies 10 bytes (AGHI + BRCL).
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# This means that loop 5 contains 4 * 6 + 0xffd8 + 4 * 4 == 0x10000 bytes
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# and is therefore (just) in range. Loop 6 is out of range.
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#
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# CHECK: brctg {{%r[0-9]+}}
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# CHECK: brctg {{%r[0-9]+}}
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# CHECK: brctg {{%r[0-9]+}}
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# CHECK: brctg {{%r[0-9]+}}
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# CHECK: brctg {{%r[0-9]+}}
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# CHECK: aghi {{%r[0-9]+}}, -1
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# CHECK: jglh
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# CHECK: aghi {{%r[0-9]+}}, -1
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# CHECK: jglh
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# CHECK: aghi {{%r[0-9]+}}, -1
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# CHECK: jglh
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branch_blocks = 8
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main_size = 0xffd8
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print 'define void @f1(i8 *%base, i64 *%counts) {'
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print 'entry:'
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for i in xrange(branch_blocks - 1, -1, -1):
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print ' %%countptr%d = getelementptr i64 *%%counts, i64 %d' % (i, i)
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print ' %%initcount%d = load i64 *%%countptr%d' % (i, i)
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print ' br label %%loop%d' % i
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print 'loop%d:' % i
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block1 = 'entry' if i == branch_blocks - 1 else 'loop%d' % (i + 1)
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block2 = 'loop0' if i == 0 else 'after%d' % (i - 1)
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print (' %%count%d = phi i64 [ %%initcount%d, %%%s ],'
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' [ %%nextcount%d, %%%s ]' % (i, i, block1, i, block2))
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a, b = 1, 1
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for i in xrange(0, main_size, 6):
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a, b = b, a + b
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offset = 4096 + b % 500000
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value = a % 256
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print ' %%ptr%d = getelementptr i8 *%%base, i64 %d' % (i, offset)
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print ' store volatile i8 %d, i8 *%%ptr%d' % (value, i)
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for i in xrange(branch_blocks):
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print ' %%nextcount%d = add i64 %%count%d, -1' % (i, i)
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print ' %%test%d = icmp ne i64 %%nextcount%d, 0' % (i, i)
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print ' br i1 %%test%d, label %%loop%d, label %%after%d' % (i, i, i)
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print ''
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print 'after%d:' % i
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print ' ret void'
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print '}'
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