[SystemZ] Register compare-and-branch support
This patch adds support for the CRJ and CGRJ instructions. Support for
the immediate forms will be a separate patch.
The architecture has a large number of comparison instructions. I think
it's generally better to concentrate on using the "best" comparison
instruction first and foremost, then only use something like CRJ if
CR really was the natual choice of comparison instruction. The patch
therefore opportunistically converts separate CR and BRC instructions
into a single CRJ while emitting instructions in ISelLowering.
llvm-svn: 182764
diff --git a/llvm/test/CodeGen/SystemZ/Large/branch-range-04.py b/llvm/test/CodeGen/SystemZ/Large/branch-range-04.py
new file mode 100644
index 0000000..3ae3ae9
--- /dev/null
+++ b/llvm/test/CodeGen/SystemZ/Large/branch-range-04.py
@@ -0,0 +1,111 @@
+# Test 64-bit COMPARE AND BRANCH in cases where the sheer number of
+# instructions causes some branches to be out of range.
+# RUN: python %s | llc -mtriple=s390x-linux-gnu | FileCheck %s
+
+# Construct:
+#
+# before0:
+# conditional branch to after0
+# ...
+# beforeN:
+# conditional branch to after0
+# main:
+# 0xffcc bytes, from MVIY instructions
+# conditional branch to main
+# after0:
+# ...
+# conditional branch to main
+# afterN:
+#
+# Each conditional branch sequence occupies 12 bytes if it uses a short
+# branch and 16 if it uses a long one. The ones before "main:" have to
+# take the branch length into account, which is 6 for short branches,
+# so the final (0x34 - 6) / 12 == 3 blocks can use short branches.
+# The ones after "main:" do not, so the first 0x34 / 12 == 4 blocks
+# can use short branches. The conservative algorithm we use makes
+# one of the forward branches unnecessarily long, as noted in the
+# check output below.
+#
+# CHECK: lgb [[REG:%r[0-5]]], 0(%r3)
+# CHECK: cgr %r4, [[REG]]
+# CHECK: jge [[LABEL:\.L[^ ]*]]
+# CHECK: lgb [[REG:%r[0-5]]], 1(%r3)
+# CHECK: cgr %r4, [[REG]]
+# CHECK: jge [[LABEL]]
+# CHECK: lgb [[REG:%r[0-5]]], 2(%r3)
+# CHECK: cgr %r4, [[REG]]
+# CHECK: jge [[LABEL]]
+# CHECK: lgb [[REG:%r[0-5]]], 3(%r3)
+# CHECK: cgr %r4, [[REG]]
+# CHECK: jge [[LABEL]]
+# CHECK: lgb [[REG:%r[0-5]]], 4(%r3)
+# CHECK: cgr %r4, [[REG]]
+# CHECK: jge [[LABEL]]
+# ...as mentioned above, the next one could be a CGRJE instead...
+# CHECK: lgb [[REG:%r[0-5]]], 5(%r3)
+# CHECK: cgr %r4, [[REG]]
+# CHECK: jge [[LABEL]]
+# CHECK: lgb [[REG:%r[0-5]]], 6(%r3)
+# CHECK: cgrje %r4, [[REG]], [[LABEL]]
+# CHECK: lgb [[REG:%r[0-5]]], 7(%r3)
+# CHECK: cgrje %r4, [[REG]], [[LABEL]]
+# ...main goes here...
+# CHECK: lgb [[REG:%r[0-5]]], 25(%r3)
+# CHECK: cgrje %r4, [[REG]], [[LABEL:\.L[^ ]*]]
+# CHECK: lgb [[REG:%r[0-5]]], 26(%r3)
+# CHECK: cgrje %r4, [[REG]], [[LABEL]]
+# CHECK: lgb [[REG:%r[0-5]]], 27(%r3)
+# CHECK: cgrje %r4, [[REG]], [[LABEL]]
+# CHECK: lgb [[REG:%r[0-5]]], 28(%r3)
+# CHECK: cgrje %r4, [[REG]], [[LABEL]]
+# CHECK: lgb [[REG:%r[0-5]]], 29(%r3)
+# CHECK: cgr %r4, [[REG]]
+# CHECK: jge [[LABEL]]
+# CHECK: lgb [[REG:%r[0-5]]], 30(%r3)
+# CHECK: cgr %r4, [[REG]]
+# CHECK: jge [[LABEL]]
+# CHECK: lgb [[REG:%r[0-5]]], 31(%r3)
+# CHECK: cgr %r4, [[REG]]
+# CHECK: jge [[LABEL]]
+# CHECK: lgb [[REG:%r[0-5]]], 32(%r3)
+# CHECK: cgr %r4, [[REG]]
+# CHECK: jge [[LABEL]]
+
+branch_blocks = 8
+main_size = 0xffcc
+
+print 'define void @f1(i8 *%base, i8 *%stop, i64 %limit) {'
+print 'entry:'
+print ' br label %before0'
+print ''
+
+for i in xrange(branch_blocks):
+ next = 'before%d' % (i + 1) if i + 1 < branch_blocks else 'main'
+ print 'before%d:' % i
+ print ' %%bstop%d = getelementptr i8 *%%stop, i64 %d' % (i, i)
+ print ' %%bcur%d = load volatile i8 *%%bstop%d' % (i, i)
+ print ' %%bext%d = sext i8 %%bcur%d to i64' % (i, i)
+ print ' %%btest%d = icmp eq i64 %%limit, %%bext%d' % (i, i)
+ print ' br i1 %%btest%d, label %%after0, label %%%s' % (i, next)
+ print ''
+
+print '%s:' % next
+a, b = 1, 1
+for i in xrange(0, main_size, 6):
+ a, b = b, a + b
+ offset = 4096 + b % 500000
+ value = a % 256
+ print ' %%ptr%d = getelementptr i8 *%%base, i64 %d' % (i, offset)
+ print ' store volatile i8 %d, i8 *%%ptr%d' % (value, i)
+
+for i in xrange(branch_blocks):
+ print ' %%astop%d = getelementptr i8 *%%stop, i64 %d' % (i, i + 25)
+ print ' %%acur%d = load volatile i8 *%%astop%d' % (i, i)
+ print ' %%aext%d = sext i8 %%acur%d to i64' % (i, i)
+ print ' %%atest%d = icmp eq i64 %%limit, %%aext%d' % (i, i)
+ print ' br i1 %%atest%d, label %%main, label %%after%d' % (i, i)
+ print ''
+ print 'after%d:' % i
+
+print ' ret void'
+print '}'