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

[Nate Begeman]

Changes in directory llvm/lib/Target/PowerPC:

README.txt updated: 1.60 -> 1.61
---
Log message:

Remove some stuff that now works


---
Diffs of the changes:  (+0 -53)

 README.txt |   53 -----------------------------------------------------
 1 files changed, 53 deletions(-)


Index: llvm/lib/Target/PowerPC/README.txt
diff -u llvm/lib/Target/PowerPC/README.txt:1.60 llvm/lib/Target/PowerPC/README.txt:1.61
--- llvm/lib/Target/PowerPC/README.txt:1.60	Fri Feb  3 16:06:45 2006
+++ llvm/lib/Target/PowerPC/README.txt	Sat Feb  4 01:29:35 2006
@@ -198,59 +198,6 @@
 
 ===-------------------------------------------------------------------------===
 
-176.gcc contains a bunch of code like this (this occurs dozens of times):
-
-int %test(uint %mode.0.i.0) {
-        %tmp.79 = cast uint %mode.0.i.0 to sbyte        ; <sbyte> [#uses=1]
-        %tmp.80 = cast sbyte %tmp.79 to int             ; <int> [#uses=1]
-        %tmp.81 = shl int %tmp.80, ubyte 16             ; <int> [#uses=1]
-        %tmp.82 = and int %tmp.81, 16711680
-        ret int %tmp.82
-}
-
-which we compile to:
-
-_test:
-        extsb r2, r3
-        rlwinm r3, r2, 16, 8, 15
-        blr
-
-The extsb is obviously dead.  This can be handled by a future thing like 
-MaskedValueIsZero that checks to see if bits are ever demanded (in this case, 
-the sign bits are never used, so we can fold the sext_inreg to nothing).
-
-I'm seeing code like this:
-
-        srwi r3, r3, 16
-        extsb r3, r3
-        rlwimi r4, r3, 16, 8, 15
-
-in which the extsb is preventing the srwi from being nuked.
-
-===-------------------------------------------------------------------------===
-
-Another example that occurs is:
-
-uint %test(int %specbits.6.1) {
-        %tmp.2540 = shr int %specbits.6.1, ubyte 11     ; <int> [#uses=1]
-        %tmp.2541 = cast int %tmp.2540 to uint          ; <uint> [#uses=1]
-        %tmp.2542 = shl uint %tmp.2541, ubyte 13        ; <uint> [#uses=1]
-        %tmp.2543 = and uint %tmp.2542, 8192            ; <uint> [#uses=1]
-        ret uint %tmp.2543
-}
-
-which we codegen as:
-
-l1_test:
-        srawi r2, r3, 11
-        rlwinm r3, r2, 13, 18, 18
-        blr
-
-the srawi can be nuked by turning the SAR into a logical SHR (the sext bits are 
-dead), which I think can then be folded into the rlwinm.
-
-===-------------------------------------------------------------------------===
-
 Compile offsets from allocas:
 
 int *%test() {