diff options
| -rw-r--r-- | llvm/test/Transforms/LoopIdiom/X86/ctlz.ll | 82 |
1 files changed, 82 insertions, 0 deletions
diff --git a/llvm/test/Transforms/LoopIdiom/X86/ctlz.ll b/llvm/test/Transforms/LoopIdiom/X86/ctlz.ll index d8daa3a9bba..0bb7d567edf 100644 --- a/llvm/test/Transforms/LoopIdiom/X86/ctlz.ll +++ b/llvm/test/Transforms/LoopIdiom/X86/ctlz.ll @@ -183,3 +183,85 @@ while.cond: ; preds = %while.cond, %entry while.end: ; preds = %while.cond ret i32 %i.0 } + +; This loop contains a volatile store. If x is initially negative, +; the code will be an infinite loop because the ashr will eventually produce +; all ones and continue doing so. This prevents the loop from terminating. If +; we convert this to a countable loop using ctlz that loop will only run 32 +; times. This is different than the infinite number of times of the original. +; FIXME: Don't transform this loop. +define i32 @foo(i32 %x) { +; LZCNT-LABEL: @foo( +; LZCNT-NEXT: entry: +; LZCNT-NEXT: [[V:%.*]] = alloca i8, align 1 +; LZCNT-NEXT: [[TOBOOL4:%.*]] = icmp eq i32 [[X:%.*]], 0 +; LZCNT-NEXT: br i1 [[TOBOOL4]], label [[WHILE_END:%.*]], label [[WHILE_BODY_LR_PH:%.*]] +; LZCNT: while.body.lr.ph: +; LZCNT-NEXT: [[TMP0:%.*]] = call i32 @llvm.ctlz.i32(i32 [[X]], i1 true) +; LZCNT-NEXT: [[TMP1:%.*]] = sub i32 32, [[TMP0]] +; LZCNT-NEXT: br label [[WHILE_BODY:%.*]] +; LZCNT: while.body: +; LZCNT-NEXT: [[TCPHI:%.*]] = phi i32 [ [[TMP1]], [[WHILE_BODY_LR_PH]] ], [ [[TCDEC:%.*]], [[WHILE_BODY]] ] +; LZCNT-NEXT: [[CNT_06:%.*]] = phi i32 [ 0, [[WHILE_BODY_LR_PH]] ], [ [[INC:%.*]], [[WHILE_BODY]] ] +; LZCNT-NEXT: [[X_ADDR_05:%.*]] = phi i32 [ [[X]], [[WHILE_BODY_LR_PH]] ], [ [[SHR:%.*]], [[WHILE_BODY]] ] +; LZCNT-NEXT: [[SHR]] = ashr i32 [[X_ADDR_05]], 1 +; LZCNT-NEXT: [[INC]] = add i32 [[CNT_06]], 1 +; LZCNT-NEXT: store volatile i8 42, i8* [[V]], align 1 +; LZCNT-NEXT: [[TCDEC]] = sub nsw i32 [[TCPHI]], 1 +; LZCNT-NEXT: [[TOBOOL:%.*]] = icmp eq i32 [[TCDEC]], 0 +; LZCNT-NEXT: br i1 [[TOBOOL]], label [[WHILE_COND_WHILE_END_CRIT_EDGE:%.*]], label [[WHILE_BODY]] +; LZCNT: while.cond.while.end_crit_edge: +; LZCNT-NEXT: [[SPLIT:%.*]] = phi i32 [ [[TMP1]], [[WHILE_BODY]] ] +; LZCNT-NEXT: br label [[WHILE_END]] +; LZCNT: while.end: +; LZCNT-NEXT: [[CNT_0_LCSSA:%.*]] = phi i32 [ [[SPLIT]], [[WHILE_COND_WHILE_END_CRIT_EDGE]] ], [ 0, [[ENTRY:%.*]] ] +; LZCNT-NEXT: ret i32 [[CNT_0_LCSSA]] +; +; NOLZCNT-LABEL: @foo( +; NOLZCNT-NEXT: entry: +; NOLZCNT-NEXT: [[V:%.*]] = alloca i8, align 1 +; NOLZCNT-NEXT: [[TOBOOL4:%.*]] = icmp eq i32 [[X:%.*]], 0 +; NOLZCNT-NEXT: br i1 [[TOBOOL4]], label [[WHILE_END:%.*]], label [[WHILE_BODY_LR_PH:%.*]] +; NOLZCNT: while.body.lr.ph: +; NOLZCNT-NEXT: br label [[WHILE_BODY:%.*]] +; NOLZCNT: while.body: +; NOLZCNT-NEXT: [[CNT_06:%.*]] = phi i32 [ 0, [[WHILE_BODY_LR_PH]] ], [ [[INC:%.*]], [[WHILE_BODY]] ] +; NOLZCNT-NEXT: [[X_ADDR_05:%.*]] = phi i32 [ [[X]], [[WHILE_BODY_LR_PH]] ], [ [[SHR:%.*]], [[WHILE_BODY]] ] +; NOLZCNT-NEXT: [[SHR]] = ashr i32 [[X_ADDR_05]], 1 +; NOLZCNT-NEXT: [[INC]] = add i32 [[CNT_06]], 1 +; NOLZCNT-NEXT: store volatile i8 42, i8* [[V]], align 1 +; NOLZCNT-NEXT: [[TOBOOL:%.*]] = icmp eq i32 [[SHR]], 0 +; NOLZCNT-NEXT: br i1 [[TOBOOL]], label [[WHILE_COND_WHILE_END_CRIT_EDGE:%.*]], label [[WHILE_BODY]] +; NOLZCNT: while.cond.while.end_crit_edge: +; NOLZCNT-NEXT: [[SPLIT:%.*]] = phi i32 [ [[INC]], [[WHILE_BODY]] ] +; NOLZCNT-NEXT: br label [[WHILE_END]] +; NOLZCNT: while.end: +; NOLZCNT-NEXT: [[CNT_0_LCSSA:%.*]] = phi i32 [ [[SPLIT]], [[WHILE_COND_WHILE_END_CRIT_EDGE]] ], [ 0, [[ENTRY:%.*]] ] +; NOLZCNT-NEXT: ret i32 [[CNT_0_LCSSA]] +; +entry: + %v = alloca i8, align 1 + %tobool4 = icmp eq i32 %x, 0 + br i1 %tobool4, label %while.end, label %while.body.lr.ph + +while.body.lr.ph: ; preds = %entry + br label %while.body + +while.body: ; preds = %while.body.lr.ph, %while.body + %cnt.06 = phi i32 [ 0, %while.body.lr.ph ], [ %inc, %while.body ] + %x.addr.05 = phi i32 [ %x, %while.body.lr.ph ], [ %shr, %while.body ] + %shr = ashr i32 %x.addr.05, 1 + %inc = add i32 %cnt.06, 1 + store volatile i8 42, i8* %v, align 1 + %tobool = icmp eq i32 %shr, 0 + br i1 %tobool, label %while.cond.while.end_crit_edge, label %while.body + +while.cond.while.end_crit_edge: ; preds = %while.body + %split = phi i32 [ %inc, %while.body ] + br label %while.end + +while.end: ; preds = %while.cond.while.end_crit_edge, %entry + %cnt.0.lcssa = phi i32 [ %split, %while.cond.while.end_crit_edge ], [ 0, %entry ] + ret i32 %cnt.0.lcssa +} + |
