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| author | Evan Cheng <evan.cheng@apple.com> | 2007-02-07 09:22:15 +0000 |
|---|---|---|
| committer | Evan Cheng <evan.cheng@apple.com> | 2007-02-07 09:22:15 +0000 |
| commit | 2ef02a220e3f949ebd18948ebb5bea34dc18b652 (patch) | |
| tree | d273e465eacea9bcafac4808337e125b90e3ee91 | |
| parent | 8bed6c968fd7164222bc0cf4b86686c88381c3b8 (diff) | |
| download | external_llvm-2ef02a220e3f949ebd18948ebb5bea34dc18b652.tar.gz external_llvm-2ef02a220e3f949ebd18948ebb5bea34dc18b652.tar.bz2 external_llvm-2ef02a220e3f949ebd18948ebb5bea34dc18b652.zip | |
New entry.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@34000 91177308-0d34-0410-b5e6-96231b3b80d8
| -rw-r--r-- | lib/Target/ARM/README-Thumb.txt | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/lib/Target/ARM/README-Thumb.txt b/lib/Target/ARM/README-Thumb.txt index af02417d12..3818d83146 100644 --- a/lib/Target/ARM/README-Thumb.txt +++ b/lib/Target/ARM/README-Thumb.txt @@ -145,3 +145,12 @@ ldr r2, [r2, #7 * 4] This is especially bad when dynamic alloca is used. The all fixed size stack objects are referenced off the frame pointer with negative offsets. See oggenc for an example. + +//===---------------------------------------------------------------------===// + +We are reserving R3 as a scratch register under thumb mode. So if it is live in +to the function, we save / restore R3 to / from R12. Until register scavenging +is done, we should save R3 to a high callee saved reg at emitPrologue time +(when hasFP is true or stack size is large) and restore R3 from that register +instead. This allows us to at least get rid of the save to r12 everytime it is +used. |