[llvm-commits] CVS: llvm/lib/Target/ARM/README.txt

Evan Cheng evan.cheng at apple.com
Fri Mar 9 11:35:08 PST 2007

Changes in directory llvm/lib/Target/ARM:

README.txt updated: 1.17 -> 1.18
Log message:

Unfinished work and ideas related to register scavenger.

Diffs of the changes:  (+14 -0)

 README.txt |   14 ++++++++++++++
 1 files changed, 14 insertions(+)

Index: llvm/lib/Target/ARM/README.txt
diff -u llvm/lib/Target/ARM/README.txt:1.17 llvm/lib/Target/ARM/README.txt:1.18
--- llvm/lib/Target/ARM/README.txt:1.17	Fri Mar  9 13:18:59 2007
+++ llvm/lib/Target/ARM/README.txt	Fri Mar  9 13:34:51 2007
@@ -427,6 +427,7 @@
 gcc generates smaller code for this function at -O2 or -Os:
 void foo(signed char* p) {
@@ -449,3 +450,16 @@
 each comparison, where there should be only one, and the condition codes
 are not remembered when the same two values are compared twice.
+More register scavenging work:
+1. Use the register scavenger to track frame index materialized into registers
+   (those that do not fit in addressing modes) to allow reuse in the same BB.
+2. Finish scavenging for Thumb.
+3. We know some spills and restores are unnecessary. The issue is once live
+   intervals are merged, they are not never split. So every def is spilled
+   and every use requires a restore if the register allocator decides the
+   resulting live interval is not assigned a physical register. It may be
+   possible (with the help of the scavenger) to turn some spill / restore
+   pairs into register copies.

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